[Mellanox] Correct shared buffer pools for drop-over-max

[stephenxs]

Why I did it

PR #26153 enabled drop-over-max for four SN5600/SN5640 SKUs, but the shared-pool adjustments are inconsistent. SN5640-C448O16 retains its original pools, and SN5600-C256S1 has different T0 and T1 values.

Work item tracking

• Microsoft ADO: N/A

How I did it

Set both ingress_lossless_pool_size and egress_lossy_pool_size in the T0 and T1 templates to the pre-change shared-pool baseline minus 10 MiB (10,485,760 bytes).

SKU	Baseline (bytes)	Adjusted pool size (bytes)
SN5600-C224O8	144129024	133643264
SN5600-C256S1	142703616	132217856
SN5640-C448O16	108270592	97784832
SN5640-C512S2	105419776	94934016

The egress-lossless capacity, XOFF, port configuration, and drop-over-max settings remain unchanged.

How to verify it

Render each SKU's T0 and T1 pool/profile macros, with and without inactive ports. Verify both adjusted shared-pool sizes, the unchanged egress-lossless capacity, and XOFF=0. Confirm each adjusted size is exactly 10,485,760 bytes below its pre-#26153 baseline.

Which release branch to backport

• 202605
• 202511

Both branches contain the inconsistent shared-pool adjustments introduced by PR #26153 and need the same correction. Validation on both target branches is pending.

Failure type: regression.

Tested branch

Public master at 9495839742 (local template validation).

Test result

• All 16 rendered pool/profile configurations passed size checks (four SKUs, two topologies, with/without inactive ports).
• Verified that only the two shared-pool assignments and copyright years change in each of eight templates.
• git diff --check passed.
• Hardware validation and public upstream CI are pending.

Description for the changelog

Correct SN5600 and SN5640 shared buffer pool sizes for drop-over-max reservation.

Link to config_db schema for YANG module changes

N/A.

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This PR has backport request for branch(es): 202605,202511.
Added label(s) for branch(es) 202605,202511.

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[mssonicbld]

This PR has backport request label(s) for branch(es): 202511,202605, but is missing required test information. Please make sure you tick the tested branch(es) in the Tested branch section and provide test evidence (e.g., 202511: <test result>) in the Test result section as well in your PR description.

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