KVM: arm64: Remove __pkvm_mark_hyp

Now that we mark memory owned by the hypervisor in the host stage-2
during __pkvm_init(), we no longer need to rely on the host to
explicitly mark the hyp sections later on.

Remove the __pkvm_mark_hyp() hypercall altogether.

Signed-off-by: Quentin Perret <qperret@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-19-qperret@google.com