Support EPDC.
E-Ink feature is supported by i.MX6DL/SL and i.MX7D.
For now this driver only supports i.MX6DL/SL, because the
i.MX7D EPDC driver needs pxp support which is not included
in U-Boot.

Support user defined logo file, if there is no logo file, it will
draw a black border around a white screen.

If need to enable EPDC, a waveform file is required to let all
work.

Since we need LCD_MONOCHROME mode for EPDC, we introduce LCD_MONOCHROME
support.

Please refer to Linux Reference Manual for how to flash WAVEFORM file.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Robby Cai <R63905@freescale.com>
Signed-off-by: Nitin Garg <nitin.garg@freescale.com>
Signed-off-by: Ye.Li <B37916@freescale.com>
(cherry picked from commit a7244f279cc3c3994bcd103f5e9a183b1075ae71)