middle-end/114734 - wrong code with expand_call_mem_ref

middle-end/114734 - wrong code with expand_call_mem_ref

When expand_call_mem_ref looks at the definition of the address
argument to eventually expand a &TARGET_MEM_REF argument together
with a masked load it fails to honor constraints imposed by SSA
coalescing decisions.  The following fixes this.

	PR middle-end/114734
	* internal-fn.cc (expand_call_mem_ref): Use
	get_gimple_for_ssa_name to get at the def stmt of the address
	argument to honor SSA coalescing constraints.