Instead of writing directly to cptr_el2, use the helper that
selects which feature trap register to write to based on the KVM
mode.

Fixes: 75c76ab5 ("KVM: arm64: Rework CPTR_EL2 programming for HVHE configuration")
Signed-off-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230724123829.2929609-7-tabba@google.comSigned-off-by: Oliver Upton <oliver.upton@linux.dev>