drm/print: Move kerneldoc next to definition

kerneldoc expects the comment next to definitions, otherwise it can't
pick up exported vs. internal stuff.

This fixes a warning from the doc build done with:

$ make DOCBOOKS="" htmldocs

Fixes: d8187177

 ("drm: add helper for printing to log or seq_file")
Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161114115825.22050-8-daniel.vetter@ffwll.ch