msm: mdss: fix dts_x modifications for atomic commit ioctls

Starting new atomic commit IOCTL implementation, driver expects user-land
to send each input layers's destination x in full panel co-ordinate system
unlike previously this was required only when source-split feature was
enabled. As an example, in dual-dsi configuration where each panel is of
1280 width then any layer going to only right panel needs to have their
dst_x at-least 1280. Now internally driver manipulates this if source-split
is enabled or not. However current implementation sends back this modified
dst_x backs to user-land which in turn comes to driver in subsequent IOCTL
calls and leads to unexpected behaviour. Fix this by sending original dst_x
back to user-land program.

Change-Id: I962cfa15e4dc7e905e42330f808edb31d33ffdf2
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>