msm/sde/rotator: disable write operation on eventlog debugfs nodes

rotator event logger creates debugfs nodes to log events and
show them to end user. Disable write operation on these nodes
because it is not required.

Change-Id: I38852e40409417bfbc0ec483795add7fdbc49268
Signed-off-by: Jayaprakash <jmadiset@codeaurora.org>