[Fix]: kernel meta retrieval for SM7X does not work (#3746)

Co-authored-by: xiongjie <[email protected]>

Author: xiaoajie738

lmdeploy/pytorch/kernels/cuda/flashattention.py

@@ -459,7 +459,7 @@ def grid(args):
     num_warps = 4
     if _nv_cap[0] < 8:
         BLOCK_M, BLOCK_N, num_warps, num_stages = _kernel_meta_sm7x(BLOCK_DK)
-    if _nv_cap[0] < 9:
+    elif _nv_cap[0] < 9:
         if _nv_cap[1] in [6, 9]:
             BLOCK_M, BLOCK_N, num_warps, num_stages = _kernel_meta_sm86(BLOCK_DK, shared_kv)
         else: