Update CK for gfx950 (#49)

(cherry picked from commit 79922930ae070e81e9a2aadf9b56b66a8d8c95b1)

Author: alugorey

aten/src/ATen/native/transformers/hip/flash_attn/ck/fmha_bwd.hpp

@@ -453,4 +453,5 @@ struct fmha_bwd_traits
     bool is_deterministic;
     // TODO: padding check is inside this api
 };
+template <int Version = 2>
 float fmha_bwd(fmha_bwd_traits, fmha_bwd_args, const ck_tile::stream_config&);