trunk/719055fbee1551db2b6efcb2d089e23c305fb8f4: Fall back to eager _scaled_mm_v2 for swizzled scale layouts (#186384)

TorchInductor _scaled_mm_v2 lowering had no template or extern path for non-trivial swizzle patterns and asserted during compilation, breaking blockwise MXFP8/NVFP4 compile tests on Blackwell.

For swizzled scale layouts, defer to the eager _scaled_mm_v2 op before mm_args. The trivial-swizzle path is unchanged.

Authored with Claude Opus 4.8.

rel:

Approved by: https://github.com/drisspg