msm: mdss: dsi: add xlog for BTA DONE and few error messages

Add xlog entry when BTA DONE interrupt is received. And add
proper error messages before panic in few places, to make it
easy to identify the reason and place of the crash.

Change-Id: Ie9e24d2caeff12601058ea3c76af4e3dca0cd09c
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>