[AMDGPU] Ensure return address is save/restored if clobbered or when function has calls

This test is to make sure the return address registers, if clobbered in the
function or when the function has calls, are save/restored irrespective of
whether the IPRA is enabled/disabled.

This test is found to be not save/restore the return address registers, when
clobbered in the function, with the corresponding downstream changes of D114652.

The test could not be reduced further as the register allocator needs enough
register pressure so that it allocates the return address registers as well.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D120922