mali: added a sanity check for the UMP framebuffer wrappers size

Even though we are primarily using the UMP buffer obtained by the
GET_UMP_SECURE_ID_SUNXI_FB ioctl, another UMP buffer obtained by
the GET_UMP_SECURE_ID_BUF1 ioctl should also span over the whole
framebuffer. Otherwise we may have troubles with the window resize
bug recovery and buffer flipping.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>