amdgcn: Consolidate atomic minmax helpers Removes most overrides Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu> Reviewer: Aaron Watry git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@347665 91177308-0d34-0410-b5e6-96231b3b80d8