ada: exp_util.adb: prevent infinite loop in case of broken code

ada: exp_util.adb: prevent infinite loop in case of broken code

A recent commit modified exp_util.adb in order to fix the selection of
Finalize subprograms in the case of untagged objects.
This introduced regressions for GNATSAS in fixedbugs by causing
GNAT2SCIL to loop over the same type over and over in case of broken
code.
We fix this by simply checking that the loop is making progress, and if
it doesn't, assume that we're done.

gcc/ada/ChangeLog:

	* exp_util.adb (Finalize_Address): Prevent infinite loop