tree-optimization/105312 - fix ISEL VCOND expansion

The following aligns ISEL VEC_COND_EXPR expansion using VCOND
with the optab query done by vector lowering.  Instead of only
allowing the signed optab to provide EQ/NE compares we allow both
here though since there seems to be no documented canonicalization.

2022-04-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105312
	* gimple-isel.cc (gimple_expand_vec_cond_expr): Query both
	VCOND and VCONDU for EQ and NE.

	* gcc.target/arm/pr105312.c: New testcase.