drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs: Demote non-kernel-doc comment blocks

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

 drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_debugfs.c:699: warning: Function parameter or member 'm' not described in 'dmub_tracebuffer_show'
 drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_debugfs.c:699: warning: Function parameter or member 'data' not described in 'dmub_tracebuffer_show'
 drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_debugfs.c:743: warning: Function parameter or member 'm' not described in 'dmub_fw_state_show'
 drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm_debugfs.c:743: warning: Function parameter or member 'data' not described in 'dmub_fw_state_show'

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: Mikita Lipski <mikita.lipski@amd.com>
Cc: Eryk Brol <eryk.brol@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/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -691,7 +691,7 @@ static ssize_t dp_phy_test_pattern_debugfs_write(struct file *f, const char __us
 	return size;
 }
 
-/**
+/*
  * Returns the DMCUB tracebuffer contents.
  * Example usage: cat /sys/kernel/debug/dri/0/amdgpu_dm_dmub_tracebuffer
  */
@@ -735,7 +735,7 @@ static int dmub_tracebuffer_show(struct seq_file *m, void *data)
 	return 0;
 }
 
-/**
+/*
  * Returns the DMCUB firmware state contents.
  * Example usage: cat /sys/kernel/debug/dri/0/amdgpu_dm_dmub_fw_state
  */