staging: android: vsoc: fix copy_from_user overrun

The `np->permission' structure is smaller than the `np' structure but
sizeof(*np) worth of data is copied in there. Fix the size passed to
copy_from_user() to avoid overrun.

Fixes: 3d2ec9dc ("staging: Android: Add 'vsoc' driver for cuttlefish.")
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>