drm/amdgpu/display/dm: add missing parameter documentation

Added a new parameter and forgot to update the documentation.

Fixes: b6f91fc183 ("drm/amdgpu/display: buffer INTERRUPT_LOW_IRQ_CONTEXT interrupt work")
Reviewed-by: Xiaogang Chen <xiaogang.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Xiaogang Chen <xiaogang.chen@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c

@@ -73,6 +73,7 @@
  * @handler_arg: Argument passed to the handler when triggered
  * @dm: DM which this handler belongs to
  * @irq_source: DC interrupt source that this handler is registered for
+ * @work: work struct
  */
 struct amdgpu_dm_irq_handler_data {
 	struct list_head list;