fbdev: imxfb: Use lcd power constants

Replace FB_BLANK_ constants with their counterparts from the
lcd subsystem. The values are identical, so there's no change
in functionality.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240906075439.98476-24-tzimmermann@suse.de


Signed-off-by: Lee Jones <lee@kernel.org>