arm64: Convert SCTLR_EL2 to sysreg infrastructure

arm64: Convert SCTLR_EL2 to sysreg infrastructure

Convert SCTLR_EL2 to the sysreg infrastructure, as per the 2025-12_rel
revision of the Registers.json file.

Note that we slightly deviate from the above, as we stick to the ARM
ARM M.a definition of SCTLR_EL2[9], which is RES0, in order to avoid
dragging the POE2 definitions...

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260202184329.2724080-2-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>