arm64: Drop SKL0/SKL1 from TCR2_EL2

arm64: Drop SKL0/SKL1 from TCR2_EL2

Despite what the documentation says, TCR2_EL2.{SKL0,SKL1} do not exist,
and the corresponding information is in the respective TTBRx_EL2. This
is a leftover from a development version of the architecture.

This change makes TCR2_EL2 similar to TCR2_EL1 in that respect.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241023145345.1613824-2-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>