KVM: arm64: Use the in-context stage-1 in __kvm_find_s1_desc_level()

KVM: arm64: Use the in-context stage-1 in __kvm_find_s1_desc_level()

Running the external_aborts selftest at EL2 leads to an ugly splat due
to the stage-1 MMU being disabled for the walked context, owing to the
fact that __kvm_find_s1_desc_level() is hardcoded to the EL1&0 regime.

Select the appropriate translation regime for the stage-1 walk based on
the current vCPU context.

Fixes: b8e625167a32 ("KVM: arm64: Add S1 IPA to page table level walker")
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>