mdss: display: use local_clock() instead of ktime for xlog

For better analysis, time stamp of xlog should synchronize with
the time stamp of printk. Use local_clock() to log time stamp.

CRs-Fixed: 673350
Change-Id: I00e456fdc35f5a85d8029d12f4507990444e2821
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>