drm/amd/amdgpu/dce_v6_0: Fix formatting and missing parameter description issues

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

 drivers/gpu/drm/amd/amdgpu/dce_v6_0.c:192: warning: Function parameter or member 'async' not described in 'dce_v6_0_page_flip'
 drivers/gpu/drm/amd/amdgpu/dce_v6_0.c:1050: warning: Cannot understand  *

Acked-by: Christian König <christian.koenig@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: Luben Tuikov <luben.tuikov@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/amdgpu/dce_v6_0.c

@@ -180,6 +180,7 @@ static void dce_v6_0_pageflip_interrupt_fini(struct amdgpu_device *adev)
  * @adev: amdgpu_device pointer
  * @crtc_id: crtc to cleanup pageflip on
  * @crtc_base: new address of the crtc (GPU MC address)
+ * @async: asynchronous flip
  *
  * Does the actual pageflip (evergreen+).
  * During vblank we take the crtc lock and wait for the update_pending
@@ -1047,7 +1048,6 @@ static u32 dce_v6_0_line_buffer_adjust(struct amdgpu_device *adev,
 
 
 /**
- *
  * dce_v6_0_bandwidth_update - program display watermarks
  *
  * @adev: amdgpu_device pointer