ACLE intrinsics: BFloat16 store (vst<n>{q}_bf16) intrinsics for AArch32

ACLE intrinsics: BFloat16 store (vst<n>{q}_bf16) intrinsics for AArch32

2020-03-06  Delia Burduv  <delia.burduv@arm.com>

	* config/arm/arm_neon.h (bfloat16x4x2_t): New typedef.
	(bfloat16x8x2_t): New typedef.
	(bfloat16x4x3_t): New typedef.
	(bfloat16x8x3_t): New typedef.
	(bfloat16x4x4_t): New typedef.
	(bfloat16x8x4_t): New typedef.
	(vst2_bf16): New.
	(vst2q_bf16): New.
	(vst3_bf16): New.
	(vst3q_bf16): New.
	(vst4_bf16): New.
	(vst4q_bf16): New.
	* config/arm/arm-builtins.c (v2bf_UP): Define.
	(VAR13): New.
	(arm_init_simd_builtin_types): Init Bfloat16x2_t eltype.
	* config/arm/arm-modes.def (V2BF): New mode.
	* config/arm/arm-simd-builtin-types.def
	(Bfloat16x2_t): New entry.
	* config/arm/arm_neon_builtins.def
	(vst2): Changed to VAR13 and added v4bf, v8bf
	(vst3): Changed to VAR13 and added v4bf, v8bf
	(vst4): Changed to VAR13 and added v4bf, v8bf
	* config/arm/iterators.md (VDXBF): New iterator.
	(VQ2BF): New iterator.
	*config/arm/neon.md (neon_vst2<mode>): Used new iterators.
	(neon_vst2<mode>): Used new iterators.
	(neon_vst3<mode>): Used new iterators.
	(neon_vst3<mode>): Used new iterators.
	(neon_vst3qa<mode>): Used new iterators.
	(neon_vst3qb<mode>): Used new iterators.
	(neon_vst4<mode>): Used new iterators.
	(neon_vst4<mode>): Used new iterators.
	(neon_vst4qa<mode>): Used new iterators.
	(neon_vst4qb<mode>): Used new iterators.

	* gcc.target/arm/simd/bf16_vstn_1.c: New test.