video: fbdev: mxsfb: Remove driver

There is a DRM version of the mxsfb driver for quite some time
at drivers/gpu/drm/mxsfb/, so there is no need to keep maintaining
the fbdev version any longer.

Remove the fbdev mxsfb driver in favour of the DRM version.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: NXP Linux Team <linux-imx@nxp.com>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>