drm/msm/dsi-staging: fix to prevent dsi-display probe failure

Move dsi_display_init call out from void returning
dsi_display_firmware_display function to handle the
return value of dsi_display_init function properly.

The fix ensures that -EPROBE_DEFER is passed back to
callstack, facilitating retry after failure.

Change-Id: I301c96994941371d274b687b56fe895d4b994863
Signed-off-by: Chirag Khurana <ckhurana@codeaurora.org>