arm64: rsi: Add RSI definitions

arm64: rsi: Add RSI definitions

The RMM (Realm Management Monitor) provides functionality that can be
accessed by a realm guest through SMC (Realm Services Interface) calls.

The SMC definitions are based on DEN0137[1] version 1.0-rel0.

[1] https://developer.arm.com/documentation/den0137/1-0rel0/

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20241017131434.40935-2-steven.price@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>