arm64/sysreg: Add CCSIDR2_EL1

CCSIDR2_EL1 is available if FEAT_CCIDX is implemented as per
DDI0487I.a.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230112023852.42012-4-akihiko.odaki@daynix.com


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>