drm/i915/selftests: Fix uninitialized variable

Static code analysis tool identified struct lrc_timestamp data as being
uninitialized and then data.ce[] is being checked for NULL/negative
value in the error path. Initializing data variable fixes the issue.

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200303142347.15696-1-aditya.swarup@intel.com