video/fbdev: Drop JZ4740 driver

The JZ4740 fbdev driver has been replaced with the ingenic-drm driver.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Paul Burton <paul.burton@mips.com>