MLK-10084 media: mxc vout: Correct black color filling for interleaved formats

In non-linear_bypass_pp and non-tiled_bypass_pp modes, the triple fbdev frame
buffer would be rendered with video frames in turn.  We need to fill all the
three frame buffers with black color before streaming on instead of filling only
one of them.

Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
(cherry picked from commit e0155001082abc2432ec54ac86f56abbbb744fd3)