Replace removed bfloat16ToBits with bit_cast (#241)

`bfloat16toBits` was removed in
[DPC++](intel/llvm#17256) to be replaced with
`bit_cast`. Should fix CI failures described
[here](#239 (comment)).

---------

Co-authored-by: Tadej Ciglarič <[email protected]>

Author: joeatodd

include/cutlass/bfloat16.h

@@ -126,7 +126,7 @@ struct alignas(2) bfloat16_t {
 
     #elif defined(CUTLASS_ENABLE_SYCL)
 
-    storage = sycl::ext::oneapi::detail::bfloat16ToBits(sycl::ext::oneapi::bfloat16(x));
+    storage = cutlass::platform::bit_cast<decltype(storage)>(sycl::ext::oneapi::bfloat16(x));
 
     #else
     uint32_t bits;