KVM: arm64: Restore POR_EL0 access to host EL0

KVM: arm64: Restore POR_EL0 access to host EL0

CPTR_EL2.E0POE was being cleared in __deactivate_cptr_traps_vhe(), which meant
that any accesses to POR_EL0 from host EL0 would trap and be reported to
userspace as an Illegal instruction. This would happen after running any VM,
regardless if it used POE or not.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Link: https://sashiko.dev/#/patchset/20260602155430.2088142-1-maz@kernel.org?part=1
Link: https://patch.msgid.link/20260604105434.2297268-1-joey.gouly@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger,kernel.org