[OpenCL] opencl-c.h: add CL 3.0 non-generic address space atomics

CL 2.0 introduced atomics and generic address space so there were
only one set of APIs for doing atomics, however since CL 3.0
makes generic address space optional, there has to be new sets
of atomic interfaces to handle that cases.

Reviewed By: Anastasia

Differential Revision: https://reviews.llvm.org/D106778