drm/amd/display/dc/dce/dmub_outbox: Convert over to kernel-doc

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dmub_outbox.c:30: warning: Cannot understand  *****************************************************************************

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Cc: Jun Lei <Jun.Lei@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dmub_outbox.c

@@ -27,19 +27,10 @@
 #include "dmub/inc/dmub_cmd.h"
 
 /**
- *****************************************************************************
- *  Function: dmub_enable_outbox_notification
- *
- *  @brief
- *		Sends inbox cmd to dmub to enable outbox1 messages with interrupt.
- *		Dmub sends outbox1 message and triggers outbox1 interrupt.
- *
- *  @param
- *		[in] dc: dc structure
- *
- *  @return
- *     None
- *****************************************************************************
+ *  dmub_enable_outbox_notification - Sends inbox cmd to dmub to enable outbox1
+ *                                    messages with interrupt. Dmub sends outbox1
+ *                                    message and triggers outbox1 interrupt.
+ * @dc: dc structure
  */
 void dmub_enable_outbox_notification(struct dc *dc)
 {