drm/msm/dsi-staging: only set nolp command when panel in LP1/LP2 mode

DSI driver sends nolp commands when DSI connector power
modes is set SDE_MODE_DPMS_ON or SDE_MODE_DPMS_OFF. This
is invalid panel configuration. It should only send nolp
commmand to panel when it is in LP1/LP2 mode.

Change-Id: Ie94eaef6899d292fd20f42c1b7ef2c7a99178d13
Signed-off-by: Yuan Zhao <yzhao@codeaurora.org>