msm: mdss: Add runtime writeback output format configuration

Set writeback output format using metadata_ioctl before
queuing buffer for write back from mdp. Default output
format is VENUS. Writeback support RGB_565, RGB_888,
ARGB_8888, XRGB_888 and VENUS as output format.

Change-Id: I788b7f54d80a592ac8da07d10f6b292c4650e46c
Signed-off-by: Beeresh Gopal <gbeeresh@codeaurora.org>
Signed-off-by: Pawan Kumar <pavaku@codeaurora.org>