fbdev/fsl-diu-fb: Output messages with fb_*() helpers

Fix cases were output helpers are called with struct fb_info.dev.
Use fb_*() helpers instead. Prepares fbdev for making struct
fb_info.dev optional.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Timur Tabi <timur@kernel.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613110953.24176-16-tzimmermann@suse.de