msm: mdss: avoid sending panel off command during TWM entry

Provide sysfs node to indicate TWM entry and do not
send panel off command when TWM entry is initiated.

Change-Id: I23b2f378ec7810dc6052c2927435bec8aab1b785
Signed-off-by: Sachin Bhayare <sachin.bhayare@codeaurora.org>