[AMDGPU] Fix function pointer argument bug in AMDGPU Propagate Attributes pass.

This patch fixes a bug in the AMDGPU Propagate Attributes pass where a call
instruction with a function pointer argument is identified as a user of the
passed function, and illegally replaces the called function of the
instruction with the function argument.

For example, given functions f and g with appropriate types, the following
illegal transformation could occur without this fix:
call void @f(void ()* @g)
-->
call void @g(void ()* @g.1)

The solution introduced in this patch is to prevent the cloning and
substitution if the instruction's called function and the function which
might be cloned do not match.

Reviewed By: arsenm, madhur13490

Differential Revision: https://reviews.llvm.org/D101847