KVM: arm64: Refactor CPACR trap bit setting/clearing to use ELx format

KVM: arm64: Refactor CPACR trap bit setting/clearing to use ELx format

When setting/clearing CPACR bits for EL0 and EL1, use the ELx
format of the bits, which covers both. This makes the code
clearer, and reduces the chances of accidentally missing a bit.

No functional change intended.

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20240603122852.3923848-9-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>