vect: Add check for BUILT_IN_NORMAL to ifcvt [PR122103]

vect: Add check for BUILT_IN_NORMAL to ifcvt [PR122103]

It was reported that some AVX10 test like
gcc.target/i386/avx10_2-vcvtbf162ibs-2.c ICEd with my
changes.  It turns out it's due to associated_internal_fn
only supporting BUILT_IN_NORMAL calls.

This adds a check for this before calling
associated_internal_fn.

Manually tested the files since they have an effective
target tests for hardware I don't have.

gcc/ChangeLog:

	PR tree-optimization/122103
	* tree-if-conv.cc (ifcvt_can_predicate): Add check for
	normal builtins.