ipa-param-manip: Be careful about a reallocating hash_map

ipa-param-manip: Be careful about a reallocating hash_map

PR 103449 revealed that when I was storing result of one hash_map
lookup into another entry in the hash_map, I was still accessing the
entry in the table, which meanwhile could get reallocated, making the
accesses invalid-after-free.

Fixed with the following, which also simplifies the return statement
which must have been true even now.

gcc/ChangeLog:

2021-11-29  Martin Liska  <mliska@suse.cz>
	    Martin Jambor  <mjambor@suse.cz>

	PR ipa/103449
	* ipa-param-manipulation.c
	(ipa_param_body_adjustments::prepare_debug_expressions): Be
	careful about hash_map reallocating itself.  Simpify a return
	which always returns true.