aarch64: Add Armv8.8-A system registers

aarch64: Add Armv8.8-A system registers

Armv8.8-A defines two new system registers: allint and icc_nmiar1_el1.
Both of them were previously unmapped.  allint supports a 0/1 immediate.
[https://developer.arm.com/documentation/ddi0595/2021-09/AArch64-Registers/ALLINT--All-Interrupt-Mask-Bit?lang=en]
[https://developer.arm.com/documentation/ddi0595/2021-09/AArch64-Registers/ICC-NMIAR1-EL1--Interrupt-Controller-Non-maskable-Interrupt-Acknowledge-Register-1?lang=en]

opcodes/
	* aarch64-opc.c (SR_V8_8): New macro.
	(aarch64_sys_regs): Add allint and icc_nmiar1_el1.
	(aarch64_pstatefields): Add allint.

gas/
	* testsuite/gas/aarch64/armv8_8-a-sysregs.s,
	* testsuite/gas/aarch64/armv8_8-a-sysregs.d: New test.
	* testsuite/gas/aarch64/armv8_8-a-sysregs-invalid.s,
	* testsuite/gas/aarch64/armv8_8-a-sysregs-invalid.l,
	* testsuite/gas/aarch64/armv8_8-a-sysregs-invalid.d: New test.