Fix PR ada/98228

This is the profiled bootstrap failure for s390x/Linux on the mainline,
which has been introduced by the modref pass but actually exposing an
existing issue in the maybe_pad_type function that is visible on s390x.

The issue is too weak a test for the addressability of the inner component.

gcc/ada/
	    Marius Hillenbrand  <mhillen@linux.ibm.com>

	PR ada/98228
	* gcc-interface/utils.c (maybe_pad_type): Test the size of the new
	packable type instead of its alignment for addressability's sake.