video: jz4740-fb: Fix LCD_CMD bit definitions

Fix the bit offsets for the LCD_CMD definitions.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>