MAINTAINERS: Update Framebuffer file patterns

Since the commit f7018c21 "video: move fbdev to drivers/video/fbdev",
all framebuffer drivers were moved to fbdev directory. Thus, file
patterns of these framebuffer drivers should be updated correctly.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>