MAINTAINERS: Add an fbdev git tree entry.

Now that there's an fbdev git tree (this is also what is pulled in to
-next), stub it in to the MAINTAINERS entry.

Signed-off-by: Paul Mundt <[e-mail]>

MAINTAINERS

···
 FRAMEBUFFER LAYER
 L:	[e-mail]
 W:	http://linux-fbdev.sourceforge.net/
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lethal/fbdev-2.6.git
 S:	Orphan
 F:	Documentation/fb/
 F:	drivers/video/fb*