atom: Consolidate cl_khr_{local,global}_int32_{base,extended}_atomics implementation

These are just atomic_* wrappers.
Switch inc, dec to use atomic_* wrappers as well.

Reviewed-By: Aaron Watry <awatry@gmail.com>
Tested-By: Aaron Watry <awatry@gmail.com>
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@335279 91177308-0d34-0410-b5e6-96231b3b80d8
21 files changed