KVM: arm64: Handle FFA_MEM_SHARE calls from the host

KVM: arm64: Handle FFA_MEM_SHARE calls from the host

Intercept FFA_MEM_SHARE/FFA_FN64_MEM_SHARE calls from the host and
transition the host stage-2 page-table entries from the OWNED state to
the SHARED_OWNED state prior to forwarding the call onto EL3.

Co-developed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230523101828.7328-7-will@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>