[SM121] Enable native block-scaled dot_scaled for DGX Spark (GB10) (#10010)

SM121 (GB10 DGX Spark) supports the same mma.sync block-scaled
instructions as SM120 (RTX 5090) but was excluded from the native
lowering path by exact compute capability checks.

Without this fix, dot_scaled on SM121 falls through to
DecomposeScaledBlocked which upcasts to bf16 — ~10 TFLOPS vs ~270 TFLOPS
with native mma.sync block-scaled FP4.

Tested on GB10 with both MXFP4 (scale_vec::2X, ue8m0) and NVFP4
(scale_vec::4X, ue4m3).


# New contributor declaration
- [ x] I am not making a trivial change, such as fixing a typo in a
comment.

- [ x] I have written a PR description following these
  [rules](https://cbea.ms/git-commit/#why-not-how).

- [ x] I have run `pre-commit run --from-ref origin/main --to-ref HEAD`.

- Select one of the following.
  - [ ] I have added tests.
    - `/test` for `lit` tests
    - `/unittest` for C++ tests
    - `/python/test` for end-to-end tests
- [ x ] This PR does not need a test because current test paths cover
the flow, though there are no GB10s in CI to verify AFAIK it does work
for me.

- Select one of the following.
  - [x ] I have not added any `lit` tests.

Author: ianbarber

lib/Dialect/TritonGPU/Transforms/AccelerateMatmul.cpp

@@ -677,7 +677,7 @@ class ScaledBlockedToMMA : public mlir::OpRewritePattern<triton::DotScaledOp> {
   mlir::LogicalResult
   matchAndRewrite(triton::DotScaledOp dotOp,
                   mlir::PatternRewriter &rewriter) const override {
-    if (computeCapability != 120)
+    if (computeCapability / 10 != 12)
       return failure();
 
     auto numCTAs = lookupNumCTAs(rewriter);
@@ -924,7 +924,7 @@ static bool mmav2SupportsFp8Operands(int computeCapability) {
   // although PTX instructions for mma v2 w/ fp8 operands exist for sm90 and
   // sm100, they are emulated as fp16 upcasts + fp16 HMMA in SASS. sm120 has
   // hardware support for fp8 operands w/ mmav2.
-  return computeCapability == 89 || computeCapability == 120;
+  return computeCapability == 89 || computeCapability / 10 == 12;
 }
 
 // promote operands of dot op if the existing combination is not natively