drm: Remove the ', ' after the function name in debug logs

Right now a debug message looks like:

  [drm:drm_ioctl], pid=860, dev=0xe200, auth=1, DRM_IOCTL_MODE_GETCRTC

That first comma looks weird as we already have ']' as a separator.
Remove it.

If anyone sees this commit message and also thinks that auth=1 isn't the
most useful info to have here, let's just say I'd happily review a patch
removing it. If I don't get annoyed enough to submit a patch, that is.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>