dev: gcdb: use post on command to add delay for SPI panel

Use post on command interface to add delay between frame transfer
to panel and backlight on panel command.

Change-Id: I7db8db664e60eb39c9fdc71752239a5a0fc08e59
Signed-off-by: Wenjun Zhang <wjzhan@codeaurora.org>
1 file changed