Separate the new FP16 instructions backported from Armv8.4-a to Armv8.2-a into a...

Separate the new FP16 instructions backported from Armv8.4-a to Armv8.2-a into a new flag order to distinguish them from the rest of the already existing optional FP16 instructions in Armv8.2-a.

The new flag "+fp16fml" is available from Armv8.2-a and implies +fp16 and is mandatory
from Armv8.4-a.

gas/

	* config/tc-arm.c (arm_ext_fp16_fml, fp16fml): New.
	(do_neon_fmac_maybe_scalar_long): Use arm_ext_fp16_fml.
	* doc/c-arm.texi (fp16, fp16fml): New.
	* testsuite/gas/arm/armv8_2-a-fp16.d (fp16): Make fp16fml.
	* testsuite/gas/arm/armv8_3-a-fp16.d (fp16): Make fp16fml.
	* testsuite/gas/arm/armv8_2-a-fp16-illegal.d (fp16): Make fp16fml.
	* testsuite/gas/arm/armv8_2-a-fp16-thumb2.d (fp16): Make fp16fml.

include/

	* opcode/arm.h: (ARM_EXT2_FP16_FML): New.
	(ARM_AEXT2_V8_4A): Add ARM_EXT2_FP16_FML.