ANDROID: KVM: arm64: Drop FOLL_FORCE when pinning guest memory pages

Passing FOLL_FORCE when pinning guest memory pages was intended to allow
the VMM to map guest memory as PROT_NONE without prohibiting access from
the guest. As it turns out, crosvm doesn't implement this, and since
the host kernel will inject a signal into the VMM on a bad access
irrespective of the stage-1 permissions, we can drop the FOLL_FORCE flag
altogether.

Bug: 226564150
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: If21091b6adf3dbe4155c5c840753c912d283b159