drm/msm/dsi-staging: optimise TE status check sequence

To check if panel is sending TE signal or not, clock and
bandwidth vote is not required. Currently in driver for
TE mode also, driver is enabling clocks and bandwidth which
is not required and might cause unnecessary MDSS wake ups.
This change optimises the same.

Change-Id: Ia00cf7a96058223e28b7bcfac144c9987f1a6513
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>