KVM: arm64: nv: Stop passing vCPU through void ptr in S2 PTW

KVM: arm64: nv: Stop passing vCPU through void ptr in S2 PTW

The stage-2 table walker passes down the vCPU as a void pointer. That
might've made sense if the walker was generic although at this point it
is clear this will only ever be used in the context of a vCPU.

Suggested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Link: https://msgid.link/20251124190158.177318-8-oupton@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>