drm: msm: dsi: add dsi device to tail of display list instead

DSI display list sequence should be consistent with device tree, so use
list_add_tail instead of list_add to insert dsi devices.

Change-Id: I11d14d663c59c8ee0d1da280f42d9315e12c2a65
Signed-off-by: Yunyun Cao <yunyunc@codeaurora.org>