fix in solib-aix.c

fix in solib-aix.c

solib_aix_bfd_open has an early "return" that doesn't run cleanups.
This fixes the problem by dropping the null_cleanup and using a later
cleanup as the master cleanup for the function.

	* solib-aix.c (solib_aix_bfd_open): Don't use a null cleanup
	for 'cleanup'; instead use a later one.