msm: mdss: fix dst_x adjustments when source split is disabled

In order to handle different use-cases, mixer ROIs and/or dst_x
of a pipe is modified and re-adjusted. In one of these use-cases, when
source split is disabled, re-adjustment was missing causing HW hangs or
unexpected layer positions. Fix these adjustments.

Change-Id: I7cda887874aad97bca16b63ca5a9eac303fa63a4
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>