ggml-org/llama.cpp b12246

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vulkan: cap scalar flash attention at 8 rows for large heads on Qualcomm (#30829)

With head sizes above 128 and KV >= 1024, scalar flash attention uses
16 rows per workgroup. On the Qualcomm Adreno driver this variant
spills registers to scratch memory (264 bytes per invocation on the
X1-85, none at 8 rows) and runs about 40x slower. The largest
test-backend-ops case then becomes a single dispatch of several
seconds, past the Windows GPU timeout, and the test never completes on
the X1 Elite.

Use at most 8 rows per workgroup on Qualcomm when hsk or hsv > 128.
Smaller heads keep 16 rows, which is faster for them on the X2 Elite.

Adreno X1-85, FLASH_ATTN_EXT hsk=256 kv=4096: nb=64 711 ms -> 17 ms,
nb=512 no result -> 125 ms; test-backend-ops completes. Adreno X2-90:
Gemma 4 E4B pp512 at depth 4096 with flash attention 81-90 -> 117 t/s.