s390: Streamline NNPA builtins with their LLVM counterparts

s390: Streamline NNPA builtins with their LLVM counterparts

For the opaque NNP-data type prefer unsigned over signed integer types.

gcc/ChangeLog:

	* config/s390/s390-builtin-types.def: Add/remove types.
	* config/s390/s390-builtins.def
	(s390_vclfnhs,s390_vclfnls,s390_vcrnfs,s390_vcfn,s390_vcnf):
	Replace type V8HI with UV8HI.

gcc/testsuite/ChangeLog:

	* gcc.target/s390/zvector/vec-nnpa-fp16-convert.c: Replace V8HI
	types with UV8HI.
	* gcc.target/s390/zvector/vec-nnpa-fp32-convert-1.c: Dito.
	* gcc.target/s390/zvector/vec_convert_from_fp16.c: Dito.
	* gcc.target/s390/zvector/vec_convert_to_fp16.c: Dito.
	* gcc.target/s390/zvector/vec_extend_to_fp32_hi.c: Dito.
	* gcc.target/s390/zvector/vec_extend_to_fp32_lo.c: Dito.
	* gcc.target/s390/zvector/vec_round_from_fp32.c: Dito.