KVM: arm64: Move vcpu WFIT flag to the state flag set

The host kernel uses the WFIT flag to remember that a vcpu has used
this instruction and wake it up as required. Move it to the state
set, as nothing in the hypervisor uses this information.

Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>