KVM: arm64: Ensure FFA ranges are page aligned

KVM: arm64: Ensure FFA ranges are page aligned

Harden the check for the constituent memory region page alignment
to prevent over-sharing when the negotiated FFA_PAGE_SIZE size is
smaller than the system PAGE_SIZE.
At the moment we only check that the size of the range is page
aligned, and truncate the address to the page boundary which can
annotate more memory than needed as being used by the FF-A.

Fixes: 436090001776 ("KVM: arm64: Handle FFA_MEM_SHARE calls from the host")
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Link: https://patch.msgid.link/20260702103848.1647249-6-sebastianene@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>