video: mmp: add pitch info in mmp_win structure

Add pitch length info of graphics/video layer, pitch is used
to represent line length in byte, the usage depends on pix_fmt.
If the fmt is YUV, the pitch[0] will be Y length,pitch[1]
will be U length, pitch[2] will be V lenth.
If the fmt is RGB, the picth[0] will be line lenth, and
pitch[1]/pitch[2] will be 0 and not be used.

Signed-off-by: Jing Xiang <jxiang@marvell.com>
Signed-off-by: Jett.Zhou <jtzhou@marvell.com>
Signed-off-by: Zhou Zhu <zzhu3@marvell.com>
Reviewed-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>