drm/msm/dsi-staging: enable panel te irq only during esd check

Panel TE irq is now enabled and disabled as part of display prepare
and unprepare respectively. This change enables and disables irq as
part of ESD check mechanism thereby saving power.

Change-Id: Iaea88fd8dd5cdcf52fdc0959aaca882b16aa6322
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>