staging: video: imx: Add BGR666 support for parallel display

Support the BGR666 format on the IPUv3 parallel display.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>