fbdev/sh7760fb: Use hardware device with dev_() output during probe

Call output helpers in the probe function with the hardware device.
The virtual fbdev device has not been initialized at that point. Also
prepares fbdev for making struct fb_info.dev optional.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613110953.24176-29-tzimmermann@suse.de