drm/amdgpu: Use drm_mode_init() for on-stack modes

Initialize on-stack modes with drm_mode_init() to guarantee
no stack garbage in the list head, or that we aren't copying
over another mode's list head.

Based on the following cocci script, with manual fixups:
@decl@
identifier M;
expression E;
@@
- struct drm_display_mode M = E;
+ struct drm_display_mode M;

@@
identifier decl.M;
expression decl.E;
statement S, S1;
@@
struct drm_display_mode M;
... when != S
+ drm_mode_init(&M, &E);
+
S1

@@
expression decl.E;
@@
- &*E
+ E

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -5684,7 +5684,7 @@ create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
 	const struct drm_connector_state *con_state =
 		dm_state ? &dm_state->base : NULL;
 	struct dc_stream_state *stream = NULL;
-	struct drm_display_mode mode = *drm_mode;
+	struct drm_display_mode mode;
 	struct drm_display_mode saved_mode;
 	struct drm_display_mode *freesync_mode = NULL;
 	bool native_mode_found = false;
@@ -5699,6 +5699,7 @@ create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
 
 	struct dc_sink *sink = NULL;
 
+	drm_mode_init(&mode, drm_mode);
 	memset(&saved_mode, 0, sizeof(saved_mode));
 
 	if (aconnector == NULL) {