[clang] Fix function pointer address space

Functions pointers should be created with program address space. This
patch introduces program address space in TargetInfo. Targets with
non-default (default is 0) address space for functions should explicitly
set this value. This patch fixes a crash on lvalue reference to function
pointer (in device code) when using oneAPI DPC++ compiler.

Differential Revision: https://reviews.llvm.org/D111566