drm: mxsfb: Print failed bus format in hex

media-bus-formats.h has them in hexadecimal as well so matching with
that file saves one conversion when debugging.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Stefan Agner <stefan@agner.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/c84b34855abbb85cd25bbb5126db302f88327640.1633959458.git.agx@sigxcpu.org