video: mxsfb: Adapt to new videomode API

commit 6cd2c7db (videomode: videomode_from_timing work) changed the name of
the function from videomode_from_timing() to videomode_from_timings().

commit 32ed6ef1

 (videomode: create enum for videomode's display flags) changed
the 'data_flags' field in videomode structure to 'flags'

Adapt to these changes in order to fix the following errors:

drivers/video/mxsfb.c:761:3: error: too many arguments to function 'videomode_from_timing'
drivers/video/mxsfb.c:761:7: error: void value not ignored as it ought to be
drivers/video/mxsfb.c:768:9: error: 'struct videomode' has no member named 'data_flags'
drivers/video/mxsfb.c:770:9: error: 'struct videomode' has no member named 'data_flags'

Also, select VIDEOMODE_HELPER instead of OF_VIDEOMODE, as this one is
deprecated.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>