[KERNELS] Skip idle_sms on AMD (#7217)

As it's not currently supported

Author: lezcano

python/triton_kernels/tests/test_matmul.py

@@ -445,6 +445,8 @@ def round_x(x, idx):
 
 
 def test_set_idle_sms():
+    if not is_cuda():
+        pytest.skip("Only supported on CUDA")
     from triton_kernels.matmul_ogs_details.opt_flags import make_opt_flags
     num_idle_sms = 24
     matmul_ogs_set_idle_sms(num_idle_sms)