arm64/sysreg: Convert SCXTNUM_EL1 to automatic generation

Convert SCXTNUM_EL1 to automatic generation as per DDI0487H.a, no
functional changes.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20220905225425.1871461-28-broonie@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>