aarch64: Add support for new SME instructions

This patch adds support for three new SME instructions: ADDSPL,
ADDSVL and RDSVL.  They behave like ADDPL, ADDVL and RDVL, but read
the streaming vector length instead of the current vector length.

opcodes/
	* aarch64-tbl.h (aarch64_opcode_table): Add ADDSPL, ADDSVL and RDSVL.
	* aarch64-dis-2.c: Regenerate.

gas/
	* testsuite/gas/aarch64/sme.s, testsuite/gas/aarch64/sme.d: Add tests
	for ADDSPL, ADDSVL and RDSVL.