[GCC][PATCH][ARM]Add ACLE intrinsics for dot product (vusdot - vector, v<us/su>dot...

[GCC][PATCH][ARM]Add ACLE intrinsics for dot product (vusdot - vector, v<us/su>dot - by element) for AArch32 AdvSIMD ARMv8.6 Extension

This patch adds the ARMv8.6 Extension ACLE intrinsics for dot product
operations (vector/by element) to the ARM back-end.

These are:
usdot (vector), <us/su>dot (by element).

The functions are optional from ARMv8.2-a as -march=armv8.2-a+i8mm and
for ARM they remain optional after as of ARMv8.6-a.

The functions are declared in arm_neon.h, RTL patterns are defined to
generate assembler and tests are added to verify and perform adequate checks.

Regression testing on arm-none-eabi passed successfully.

gcc/ChangeLog:

2020-02-11  Stam Markianos-Wright  <stam.markianos-wright@arm.com>

	* config/arm/arm-builtins.c (enum arm_type_qualifiers):
	(USTERNOP_QUALIFIERS): New define.
	(USMAC_LANE_QUADTUP_QUALIFIERS): New define.
	(SUMAC_LANE_QUADTUP_QUALIFIERS): New define.
	(arm_expand_builtin_args): Add case ARG_BUILTIN_LANE_QUADTUP_INDEX.
	(arm_expand_builtin_1): Add qualifier_lane_quadtup_index.
	* config/arm/arm_neon.h (vusdot_s32): New.
	(vusdot_lane_s32): New.
	(vusdotq_lane_s32): New.
	(vsudot_lane_s32): New.
	(vsudotq_lane_s32): New.
	* config/arm/arm_neon_builtins.def (usdot, usdot_lane,sudot_lane): New.
	* config/arm/iterators.md (DOTPROD_I8MM): New.
	(sup, opsuffix): Add <us/su>.
	* config/arm/neon.md (neon_usdot, <us/su>dot_lane: New.
	* config/arm/unspecs.md (UNSPEC_DOT_US, UNSPEC_DOT_SU): New.

gcc/testsuite/ChangeLog:

2020-02-11  Stam Markianos-Wright  <stam.markianos-wright@arm.com>

	* gcc.target/arm/simd/vdot-2-1.c: New test.
	* gcc.target/arm/simd/vdot-2-2.c: New test.
	* gcc.target/arm/simd/vdot-2-3.c: New test.
	* gcc.target/arm/simd/vdot-2-4.c: New test.