Fix handling of ICF_NOVOPS in ipa-modref

Fix handling of ICF_NOVOPS in ipa-modref

As shown in somewhat convoluted testcase, ipa-modref is mistreating
ECF_NOVOPS as "having no side effects".  This come from time when
modref cared only about memory accesses and thus it was possible to
shortcut on it.

This patch removes (hopefully) all those bad shortcuts.
Bootstrapped/regtested x86_64-linux, comitted.

gcc/ChangeLog:

	PR ipa/109985

	* ipa-modref.cc (modref_summary::useful_p): Fix handling of ECF_NOVOPS.
	(modref_access_analysis::process_fnspec): Likevise.
	(modref_access_analysis::analyze_call): Likevise.
	(propagate_unknown_call): Likevise.
	(modref_propagate_in_scc): Likevise.
	(modref_propagate_flags_in_scc): Likewise.
	(ipa_merge_modref_summary_after_inlining): Likewise.