match.pd: When simplifying BFR of an insert, require a mode precision integral type...

match.pd: When simplifying BFR of an insert, require a mode precision integral type [PR108688]

The same problem as PR 88739 has crept in but
this time in match.pd when simplifying bit_field_ref of
an bit_insert. That is we are generating a BIT_FIELD_REF
of a non-mode-precision integral type.

	PR tree-optimization/108688
	* match.pd (bit_field_ref [bit_insert]): Avoid generating
	BIT_FIELD_REFs of non-mode-precision integral operands.

	* gcc.c-torture/compile/pr108688-1.c: New test.