drm: msm: dsi-staging: Fix dsi-te-using-wd during POMS

Currently, in POMS case TE register is getting programmed
before is_te_using_watchdog_timer flag is set. So, on
switching the mode, since the TE register is not programmed
properly, TE check fails. This change sets the flag
is_te_using_watchdog_timer before register programming.

Change-Id: I8ff39d8d5ab7391fca94d7678301dd46402809d5
Signed-off-by: Lipsa Rout <lrout@codeaurora.org>