[AArch32] ACLE intrinsics bfloat16 vmmla and vfma<b/t> for AArch32 AdvSIMD

[AArch32] ACLE intrinsics bfloat16 vmmla and vfma<b/t> for AArch32 AdvSIMD

This patch adds the ARMv8.6 ACLE intrinsics for vmmla, vfmab and vfmat
as part of the BFloat16 extension.
(https://developer.arm.com/docs/101028/latest.)
The intrinsics are declared in arm_neon.h and the RTL patterns are
defined in neon.md.
Two new tests are added to check assembler output and lane indices.

2020-03-05  Delia Burduv  <delia.burduv@arm.com>

	* config/arm/arm_neon.h (vbfmmlaq_f32): New.
	(vbfmlalbq_f32): New.
	(vbfmlaltq_f32): New.
	(vbfmlalbq_lane_f32): New.
	(vbfmlaltq_lane_f32): New.
	(vbfmlalbq_laneq_f32): New.
	(vbfmlaltq_laneq_f32): New.
	* config/arm/arm_neon_builtins.def (vmmla): New.
	(vfmab): New.
	(vfmat): New.
	(vfmab_lane): New.
	(vfmat_lane): New.
	(vfmab_laneq): New.
	(vfmat_laneq): New.
	* config/arm/iterators.md (BF_MA): New int iterator.
	(bt): New int attribute.
	(VQXBF): Copy of VQX with V8BF.
	* config/arm/neon.md (neon_vmmlav8bf): New insn.
	(neon_vfma<bt>v8bf): New insn.
	(neon_vfma<bt>_lanev8bf): New insn.
	(neon_vfma<bt>_laneqv8bf): New expand.
	(neon_vget_high<mode>): Changed iterator to VQXBF.
	* config/arm/unspecs.md (UNSPEC_BFMMLA): New UNSPEC.
	(UNSPEC_BFMAB): New UNSPEC.
	(UNSPEC_BFMAT): New UNSPEC.

2020-03-05  Delia Burduv  <delia.burduv@arm.com>

	* gcc.target/arm/simd/bf16_ma_1.c: New test.
	* gcc.target/arm/simd/bf16_ma_2.c: New test.
	* gcc.target/arm/simd/bf16_mmla_1.c: New test.