i386, ipa-modref: Comment spelling fix

This patch fixes spelling of prefer (misspelled as preffer).

2021-12-04  Jakub Jelinek  <jakub@redhat.com>

	* config/i386/x86-tune.def (X86_TUNE_PARTIAL_REG_DEPENDENCY): Fix
	comment typo, Preffer -> prefer.
	* ipa-modref-tree.c (modref_access_node::closer_pair_p): Likewise.