drm/msm/sde: match xlog features in evtlog

Upgrade event log facility with xlog feature set which supports
variable arguments and other features required. evtlog now
registers debugfs at /sys/kernel/debug/dri/0/evtlog. It can be
enabled by echo 1 into the enable node, and dumped using the
dump node. Move evtlog support into sde layer since only sde
uses it.

Change-Id: I51f8577a0e626ab53601e07a16cefe8da90125e1
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>