defconfig: msm8994: enable display driver xlog debug

Enable display driver xlog debugging feature.
This feature enable: MDSS registers dump during
display driver errors, panic in major errors and
add logging of events in some key functions.
Events are logged in an internal ring buffer
and only dumped during errors.

Change-Id: I8eb1713f476f637b559cfec463f249ca4ad74db1
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>