middle-end/118692 - ICE with out-of-bound ref expansion

The following guards the BIT_FIELD_REF expansion fallback for
MEM_REFs of entities expanded to register (or constant) further,
avoiding large out-of-bound offsets by, when the access does not
overlap the base object, expanding the offset as if it were zero.

	PR middle-end/118692
	* expr.cc (expand_expr_real_1): When expanding a MEM_REF
	as BIT_FIELD_REF avoid large offsets for accesses not
	overlapping the base object.

	* gcc.dg/pr118692.c: New testcase.