drm/msm/dsi-staging: fix mem leak issue in ESD debugfs

There is a potential memory leak in ESD debugfs implementation,
in case if panel ESD trigger fails. This change fixes the same.

Change-Id: I6a136aad71aa5561709d539afc13d6591bc50d1f
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>