aarch64: Add new data cache maintenance operations

aarch64: Add new data cache maintenance operations

This patch adds support to two new system registers (CIPAPA, CIGDPAPA) in
conjunction with DC instruction. This change is part of RME (Realm Management
Extension).

gas/ChangeLog:

2021-04-19  Przemyslaw Wirkus  <przemyslaw.wirkus@arm.com>

	* testsuite/gas/aarch64/rme.d: Update test.
	* testsuite/gas/aarch64/rme.s: Update test.

opcodes/ChangeLog:

2021-04-19  Przemyslaw Wirkus  <przemyslaw.wirkus@arm.com>

	* aarch64-opc.c: Add new register (CIPAPA, CIGDPAPA) support for
	DC instruction.