build: remove Nephos platform support

[zedzean]

Why I did it

Retire the Nephos platform and its device definitions, build rules, and runtime wiring as proposed in sonic-net/SONiC#2465. HLD review and component-owner sign-off are pending; please keep this draft until those are resolved. Historical release artifacts and shared platform behavior are unaffected.

Work item tracking

• Microsoft ADO (number only): N/A

How I did it

Remove the Nephos platform directory, seven associated device directories, build/CI references and Nephos-only runtime branches. Remove the obsolete nps_dev/nps_netif fallbacks from Clounix while retaining its own modules and service behavior. Pin the companion cleanups: sonic-net/sonic-swss#4956, sonic-net/sonic-sairedis#2099, sonic-net/sonic-utilities#4893, and sonic-net/sonic-platform-vpp#297. Those submodule commits must be available before this PR can land. The SWSS pointer was subsequently aligned to the current upstream submodule baseline without changing the Nephos cleanup.

Removed directories and why

• platform/nephos/: Nephos-only build rules, SAI and syncd packaging, and kernel/platform modules are no longer used once this ASIC platform is retired.
• device/accton/x86_64-accton_as7116_54x-r0/: the AS7116-54X definition, port and QoS configuration, and platform plugins target Nephos only. Other Accton devices remain.
• device/cig/: its only device directories were x86_64-cig_cs5435_54p-r0/, x86_64-cig_cs6436_54p-r0/, and x86_64-cig_cs6436_56p-r0/. All three are Nephos SKUs, so the vendor directory disappears as well.
• device/ingrasys/x86_64-ingrasys_s9130_32x-r0/ and device/ingrasys/x86_64-ingrasys_s9230_64x-r0/: these board definitions, port and QoS configuration, and platform plugins are Nephos-specific. Other Ingrasys devices remain.
• device/pegatron/: its only device directory was x86_64-pegatron_porsche-r0/, a Nephos-only SKU, so the vendor directory disappears too.

How to verify it

At buildimage commit 5b39ecd, run make configure PLATFORM=vs and make SONIC_BUILD_JOBS=32 target/sonic-vs.img.gz. The VS build completed. gzip -t passed for the BIOS and UEFI images and affected VS containers; qemu-img check on the decompressed BIOS QCOW2 reported no errors; the rootfs has a valid SquashFS superblock and the Docker manifest contains the expected VS containers. A disposable KVM guest booted the BIOS image through first-boot platform setup; the database, SWSS/orchagent, syncd and BGP services were up, and all 32 VS interfaces reported up. Commit af7069b aligns the SWSS pointer and merge commit dd20188 incorporates newer upstream master; CI still needs to validate the combined tip. git diff --check and a merge-tree check against current master pass. The full platform_asic_checker has a virtual-device failure also present at the base revision.

Which release branch to backport (provide reason below if selected)

None.

Tracking issue/work item for backport/cherry-pick request (GitHub issue or Microsoft ADO): N/A
Failure type: N/A

Tested branch

• master (base e9552ab, buildimage commit 5b39ecd)

Test result

VS image build succeeded; gzip, QCOW2 and SquashFS structural checks passed. The guest booted and essential services were up. The updated upstream tip remains for CI and owner review.

Description for the changelog

Remove Nephos platform build and runtime support.

Link to config_db schema for YANG module changes

N/A; no YANG schema changes.

A picture of a cute animal (not mandatory but encouraged)

N/A.

[mssonicbld]

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