[ARM] Match fminnum/fmaxnum for vector vminnm/vmaxnm instead of an intrinsic

Lower the intrinsic to a FMINNUM/FMAXNUM node and select that instead. This is important because soon SDAG will be able to select FMINNUM/FMAXNUM itself, so we need an integrated lowering path between SDAG and intrinsics.

NFCI.

llvm-svn: 244592