MLK-16137 video: fbdev: add defer probe for mxs framebuffer

MLK-16137 video: fbdev: add defer probe for mxs framebuffer

When mxs framebuffer probes, the DISPDRV (here is MIPI DSI driver) is likely
not ready, then mxsfb_dispdrv_init() will fail which in turn causes framebuffer
dirver probe fails. Add the defer probe schema for second probe later to fix it.

Signed-off-by: Oliver Brown <oliver.brown@nxp.com>
Signed-off-by: Robby Cai <robby.cai@nxp.com>
Reviewed-by: Fancy Fang <chen.fang@nxp.com>