[AArch64][SVE 16/32] Use specific insert/extract methods for fpimm

[AArch64][SVE 16/32] Use specific insert/extract methods for fpimm

FPIMM used the normal "imm" insert/extract methods, with a specific
test for FPIMM in the extract method.  SVE needs to use the same
extractors, so rather than add extra checks for specific operand types,
it seemed cleaner to use a separate insert/extract method.

opcodes/
	* aarch64-tbl.h (AARCH64_OPERNADS): Use fpimm rather than imm
	for FPIMM.
	* aarch64-asm.h (ins_fpimm): New inserter.
	* aarch64-asm.c (aarch64_ins_fpimm): New function.
	* aarch64-asm-2.c: Regenerate.
	* aarch64-dis.h (ext_fpimm): New extractor.
	* aarch64-dis.c (aarch64_ext_imm): Remove fpimm test.
	(aarch64_ext_fpimm): New function.
	* aarch64-dis-2.c: Regenerate.