drm/drm_print: correct format problem

[why & how]
__drm_dbg() parameter set format is wrong and not aligned with the
format under CONFIG_DRM_USE_DYNAMIC_DEBUG is on. Fix it.

Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>