backlight: lcd: Test against struct fb_info.lcd_dev

backlight: lcd: Test against struct fb_info.lcd_dev

Add struct fb_info.lcd_dev for fbdev drivers to store a reference to
their lcd device. Update the lcd's fb_notifier_callback() to test for
this field. The lcd module can now detect if an lcd device belongs to
an fbdev device.

This works similar to the bl_dev for backlights and will allow for
the removal of the check_fb callback from several fbdev driver's lcd
devices.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240906075439.98476-3-tzimmermann@suse.de
Signed-off-by: Lee Jones <lee@kernel.org>