[clang] Allow fp in atomic fetch max/min builtins

[clang] Allow fp in atomic fetch max/min builtins

LLVM IR already allows floating point type in atomicrmw.
Update clang atomic fetch max/min builtins to accept
floating point type like we did for fetch add/sub.

Reviewed by: Artem Belevich

Differential Revision: https://reviews.llvm.org/D150985

Fixes: SWDEV-401056