[ARM][GAS] ARMv8.2 should enable ARMv8.1 NEON instructions.

[ARM][GAS] ARMv8.2 should enable ARMv8.1 NEON instructions.

GAS fails to recognize march=armv8.2-a as a superset of march=armv8.1-a
when assembling NEON instructions. The patch corrects this, making
-march=armv8.2-a -mfpu=neon-fp-armv8 enable the NEON intructions
introduced with ARMv8.1-A.

include/
2016-06-30  Matthew Wahab  <matthew.wahab@arm.com>

	* opcode/arm.h (ARM_ARCH_V8_2a): Add FPU_NEON_EXT_RDMA to the set
	of enabled FPU features.

gas/
2016-06-30  Matthew Wahab  <matthew.wahab@arm.com>

	* testsuite/gas/arm/armv8_2+rdma.d: New.