[CK] Fix gptoss sink (#4313)

## Motivation

This PR removes conditional logic for handling infinity values in the
sink mechanism across multiple FMHA pipeline implementations, defaulting
sink_size to 0 and adding a constraint in the kernel selection logic.

## Technical Details

Changes:

Removed __builtin_isinf_sign(sink_v) checks and conditional
initialization of LSE accumulators across 7 pipeline files
Added default initialization (= 0) for sink_size in 4 argument structs
Added F_sink == "f" constraint to kernel compatibility checking

## Test Plan

Local test

## Test Result

passed

## Submission Checklist

- [x] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

---------

Signed-off-by: Linjun-AMD <Jun.Lin@amd.com>
Co-authored-by: systems-assistant[bot] <systems-assistant[bot]@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Illia Silin <98187287+illsilin@users.noreply.github.com>
Co-authored-by: Po Yen Chen <PoYen.Chen@amd.com>

example/ck_tile/01_fmha/codegen/ops/fmha_fwd.py

@@ -1254,6 +1254,7 @@ def get_product(receipt: int) -> Product:
             cond &= kernel_ctx.pipeline.F_bias in ["no", "alibi"]
             cond &= kernel_ctx.pipeline.F_qscale == "no"
             cond &= kernel_ctx.pipeline.F_skip == "f"
+            cond &= kernel_ctx.pipeline.F_sink == "f"
             return cond
 
         return Product(name="Flash attention integration", rule=fit)