## Motivation
FMHA codegen had incorrect dispatch behavior in group mode. Two root
causes:
1. Wrong field names in dispatch conditions — Used batch-mode fields
(seqlen_q, seqlen_k) instead of group-mode fields (max_seqlen_q,
max_seqlen_k), causing wrong kernel selection at runtime on gfx950.
2. Missing kernel variants — Group mode was overly filtered out from
smaller-tile specializations (bwd) and lacked spatial-padding pipeline
variants on gfx950 (fwd).
gfx942 don't support trload pipeline.
## Technical Details
fmha_bwd.py:
- max_seq_q_cond and extra_cond now emit t.max_seqlen_q / t.max_seqlen_k
for group mode.
- Relaxed kernel filtering: group mode no longer skips tiles with
max_seq_q != 0.
fmha_fwd.py:
- get_bm0_cond emits a.max_seqlen_q for group mode tile-size dispatch.
- Added two qr_async_trload pipeline variants with spatial padding for
gfx950 group mode.
## Test Plan
Triggering AITER CI job:
## Submission Checklist
- [ x] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.
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