Add IT6263 LVDS to HDMI card panel parameters to ARM2 boards. And enable
the DPUv1 driver and relevant settings for splash screen.

At default we set the environment variable "panel=NULL" to disable
the display output since it needs display adapter card to plug into the
board. Change the "panel=it6263" to enable it.

Signed-off-by: Ye Li <ye.li@nxp.com>