target: msm8996: add dsi swap feature on top of split mode

User can enable dsi swap feature via special fastboot command.
After it's on, display logo will be splitted and swapped on both
DSI outputs.

CRs-Fixed: 2266483
Change-Id: I5daed3903167c7b06125494be6d1426bbc94d9c2
Signed-off-by: Guchun Chen <guchunc@codeaurora.org>