tree-optimization/111807 - ICE in verify_sra_access_forest

tree-optimization/111807 - ICE in verify_sra_access_forest

The following addresses build_reconstructed_reference failing to
build references with a different offset than the models and thus
the caller conditional being off.  This manifests when attempting
to build a ref with offset 160 from the model BIT_FIELD_REF <l_4827[9], 8, 0>
onto the same base l_4827 but the models offset being 288.  This
cannot work for any kind of ref I can think of, not just with
BIT_FIELD_REFs.

	PR tree-optimization/111807
	* tree-sra.cc (build_ref_for_model): Only call
	build_reconstructed_reference when the offsets are the same.

	* gcc.dg/torture/pr111807.c: New testcase.