arm64: add ARMv8.2 id_aa64mmfr2 boiler plate

ARMv8.2 adds a new feature register id_aa64mmfr2. This patch adds the
cpu feature boiler plate used by the actual features in later patches.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/cpu.h

@@ -36,6 +36,7 @@ struct cpuinfo_arm64 {
 	u64		reg_id_aa64isar1;
 	u64		reg_id_aa64mmfr0;
 	u64		reg_id_aa64mmfr1;
+	u64		reg_id_aa64mmfr2;
 	u64		reg_id_aa64pfr0;
 	u64		reg_id_aa64pfr1;