[BE] Check that swizzle arguments are passed to the call (pytorch#167869)

Otherwise is causes null pointer deref
Pull Request resolved: pytorch#167869
Approved by: https://github.com/slayton58, https://github.com/Skylion007
ghstack dependencies: pytorch#167868

Author: malfet

aten/src/ATen/native/cuda/GroupedBlas.cpp

@@ -607,6 +607,8 @@ _scaled_grouped_mm_cuda_v2(
       // scale shape checks
       _check_scales_blocked(mat_a, scale_a[0], 0 /* dim */, 0 /* arg_idx */);
       _check_scales_blocked(mat_b, scale_b[0], 1 /* dim */, 1 /* arg_idx */);
+      // swizze checks
+      TORCH_CHECK_VALUE(swizzle_a_enum.size() == 1 && swizzle_b_enum.size() == 1, "Expected single swizzle argument");
       return _mx8_mx8_bf16_grouped_mm_fbgemm(
           mat_a,
           mat_b,