[libclc] [libclc] Move fp16 pragma guards out of header file (PR #122751)

[Fraser Cormack via cfe-commits]

================
@@ -207,10 +207,6 @@
     return BUILTIN(x);                                                         \
   }
 
-#ifdef cl_khr_fp16
-
-#pragma OPENCL EXTENSION cl_khr_fp16 : enable
-
 #define _CLC_DEFINE_UNARY_BUILTIN_FP16(FUNCTION)                               \
   _CLC_DEF _CLC_OVERLOAD half FUNCTION(half x) {                               \
     return (half)FUNCTION((float)x);                                           \
----------------
frasercrmck wrote:

True. It wouldn't solve the problem of other headers potentially disabling the pragmas, so we'd still need (or prefer) users to enable pragmas at the "call sites". But as a matter of principle I'm happy to do as you suggest.

https://github.com/llvm/llvm-project/pull/122751