drm/amd/display: Remove redundant null checks

The null checks for aconnector and aconnector->dc_link and
stream redundant as they were already dereferenced previously
as reported by Coverity; therefore the null checks are removed.

This fixes 4 REVERSE_INULL issues reported by Coverity.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -3180,7 +3180,7 @@ static int dm_resume(void *handle)
 		 * this is the case when traversing through already created end sink
 		 * MST connectors, should be skipped
 		 */
-		if (aconnector && aconnector->mst_root)
+		if (aconnector->mst_root)
 			continue;
 
 		mutex_lock(&aconnector->hpd_lock);
@@ -6422,13 +6422,13 @@ static void apply_dsc_policy_for_stream(struct amdgpu_dm_connector *aconnector,
 	dc_dsc_policy_set_enable_dsc_when_not_needed(
 		aconnector->dsc_settings.dsc_force_enable == DSC_CLK_FORCE_ENABLE);
 
-	if (aconnector->dc_link && sink->sink_signal == SIGNAL_TYPE_EDP &&
+	if (sink->sink_signal == SIGNAL_TYPE_EDP &&
 	    !aconnector->dc_link->panel_config.dsc.disable_dsc_edp &&
 	    dc->caps.edp_dsc_support && aconnector->dsc_settings.dsc_force_enable != DSC_CLK_FORCE_DISABLE) {
 
 		apply_dsc_policy_for_edp(aconnector, sink, stream, dsc_caps, max_dsc_target_bpp_limit_override);
 
-	} else if (aconnector->dc_link && sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT) {
+	} else if (sink->sink_signal == SIGNAL_TYPE_DISPLAY_PORT) {
 		if (sink->link->dpcd_caps.dongle_type == DISPLAY_DONGLE_NONE) {
 			if (dc_dsc_compute_config(aconnector->dc_link->ctx->dc->res_pool->dscs[0],
 						dsc_caps,

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

@@ -1420,7 +1420,7 @@ static ssize_t trigger_hotplug(struct file *f, const char __user *buf,
 	uint8_t param_nums = 0;
 	bool ret = false;
 
-	if (!aconnector || !aconnector->dc_link)
+	if (!aconnector->dc_link)
 		return -EINVAL;
 
 	if (size == 0)

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

@@ -807,9 +807,6 @@ bool dm_helpers_dp_write_dsc_enable(
 	uint8_t enable_passthrough = enable ? DSC_PASSTHROUGH : DSC_DISABLE;
 	uint8_t ret = 0;
 
-	if (!stream)
-		return false;
-
 	if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST) {
 		if (!aconnector->dsc_aux)
 			return false;