ENGR00180348 EPDC: invalid data when width is 2048 or greater

ENGR00180348 EPDC: invalid data when width is 2048 or greater

This patch works around the 6DLS and 6SL chip errata:
ERR005313 EPDC: Incorrect data fetched when the buffer update width is
2048 pixels or greater

This patch breaks large updates into multiple updates, which works
around the problem on both 6DSL and 6SL. This patch does not use the
Group Update feature, which may improve things further on 6SL.

This patch does not include for support for any particular large panel.
It was tested on ED09705 (2400x1650). Support for ED09705 is
available in a separate patch.

Signed-off-by: Michael Minnick <michael.minnick@freescale.com>