AVX512FP16: Add testcase for vaddph/vsubph/vmulph/vdivph.
gcc/testsuite/ChangeLog:
* gcc.target/i386/avx512fp16-helper.h: New header file for
FP16 runtime test.
* gcc.target/i386/avx512fp16-vaddph-1a.c: New test.
* gcc.target/i386/avx512fp16-vaddph-1b.c: Ditto.
* gcc.target/i386/avx512fp16-vdivph-1a.c: Ditto.
* gcc.target/i386/avx512fp16-vdivph-1b.c: Ditto.
* gcc.target/i386/avx512fp16-vmulph-1a.c: Ditto.
* gcc.target/i386/avx512fp16-vmulph-1b.c: Ditto.
* gcc.target/i386/avx512fp16-vsubph-1a.c: Ditto.
* gcc.target/i386/avx512fp16-vsubph-1b.c: Ditto.
* gcc.target/i386/avx512fp16vl-vaddph-1a.c: Ditto.
* gcc.target/i386/avx512fp16vl-vaddph-1b.c: Ditto.
* gcc.target/i386/avx512fp16vl-vdivph-1a.c: Ditto.
* gcc.target/i386/avx512fp16vl-vdivph-1b.c: Ditto.
* gcc.target/i386/avx512fp16vl-vmulph-1a.c: Ditto.
* gcc.target/i386/avx512fp16vl-vmulph-1b.c: Ditto.
* gcc.target/i386/avx512fp16vl-vsubph-1a.c: Ditto.
* gcc.target/i386/avx512fp16vl-vsubph-1b.c: Ditto.