ROCm: Add gfx950 (MI355X/CDNA4) to is_cdna() (#4051)

MI355X (gfx950) has the same 1024-thread workgroup limit as MI300X (gfx942),
but was missing from is_cdna(), causing all Triton kernels to use num_warps=32
(2048 threads) instead of 16 (1024 threads), resulting in OutOfResources crash.

Tested on: 8x AMD Instinct MI355X (gfx950), ROCm 7.1

unsloth/kernels/utils.py

@@ -82,6 +82,7 @@ def is_cdna():
         "gfx940",
         "gfx941",
         "gfx942",
+        "gfx950",  # CDNA4 (MI350/MI355X)
     )