Rename the driver from "xf86-video-sunxifb" to "xf86-video-fbturbo"

Because a wide range of embedded ARM devices are actually supported
(Allwinner A1X/A20, Raspberry Pi, ODROID-X, Rockchip, ...) and
are getting some sort of performance improvement and/or hardware
acceleration, the DDX driver needs a vendor neutral name.

Resolves https://github.com/ssvb/xf86-video-fbturbo/issues/10

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