arm: Make more use of the new mode macros

arm: Make more use of the new mode macros

As Christophe pointed out, my r11-3522 patch didn't in fact fix
all of the armv8_2-fp16-arith-2.c failures introduced by allowing
FP16 vectorisation without -funsafe-math-optimizations.  I must have
only tested the final patch on my usual arm-linux-gnueabihf bootstrap,
which it turns out treats the test as unsupported.

The focus of the original patch was to use mode macros for
patterns that are shared between Advanced SIMD, iwMMXt and MVE.
This patch uses the mode macros for general neon.md patterns too.

gcc/
	* config/arm/neon.md (*sub<VDQ:mode>3_neon): Use the new mode macros
	for the insn condition.
	(sub<VH:mode>3, *mul<VDQW:mode>3_neon): Likewise.
	(mul<VDQW:mode>3add<VDQW:mode>_neon): Likewise.
	(mul<VH:mode>3add<VH:mode>_neon): Likewise.
	(mul<VDQW:mode>3neg<VDQW:mode>add<VDQW:mode>_neon): Likewise.
	(fma<VCVTF:mode>4, fma<VH:mode>4, *fmsub<VCVTF:mode>4): Likewise.
	(quad_halves_<code>v4sf, reduc_plus_scal_<VD:mode>): Likewise.
	(reduc_plus_scal_<VQ:mode>, reduc_smin_scal_<VD:mode>): Likewise.
	(reduc_smin_scal_<VQ:mode>, reduc_smax_scal_<VD:mode>): Likewise.
	(reduc_smax_scal_<VQ:mode>, mul<VH:mode>3): Likewise.
	(neon_vabd<VF:mode>_2, neon_vabd<VF:mode>_3): Likewise.
	(fma<VH:mode>4_intrinsic): Delete.
	(neon_vadd<VCVTF:mode>): Use the new mode macros to decide which
	form of instruction to generate.
	(neon_vmla<VDQW:mode>, neon_vmls<VDQW:mode>): Likewise.
	(neon_vsub<VCVTF:mode>): Likewise.
	(neon_vfma<VH:mode>): Generate the main fma<mode>4 form instead
	of using fma<mode>4_intrinsic.

gcc/testsuite/
	* gcc.target/arm/armv8_2-fp16-arith-2.c (float16_t): Use _Float16_t
	rather than __fp16.
	(float16x4_t, float16x4_t): Likewise.
	(fp16_abs): Use __builtin_fabsf16.