drm/amd/display: Remove redundant checks for pipe_ctx->stream

[WHAT & HOW]
The null checks for pipe_ctx->stream and pipe_ctx->stream_res.tg
are redundant as they were already dereferenced previously, as
reported by Coverity; therefore the null checks are removed.

This fixes 6 REVERSE_INULL issues reported by Coverity.
Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c

@@ -974,8 +974,8 @@ enum dc_status dcn20_enable_stream_timing(
 	/* TODO enable stream if timing changed */
 	/* TODO unblank stream if DP */
 
-	if (pipe_ctx->stream && dc_state_get_pipe_subvp_type(context, pipe_ctx) == SUBVP_PHANTOM) {
-		if (pipe_ctx->stream_res.tg && pipe_ctx->stream_res.tg->funcs->phantom_crtc_post_enable)
+	if (dc_state_get_pipe_subvp_type(context, pipe_ctx) == SUBVP_PHANTOM) {
+		if (pipe_ctx->stream_res.tg->funcs->phantom_crtc_post_enable)
 			pipe_ctx->stream_res.tg->funcs->phantom_crtc_post_enable(pipe_ctx->stream_res.tg);
 	}
 
@@ -1827,8 +1827,7 @@ static void dcn20_update_dchubp_dpp(
 	if (pipe_ctx->update_flags.bits.enable)
 		hubp->funcs->set_blank(hubp, false);
 	/* If the stream paired with this plane is phantom, the plane is also phantom */
-	if (pipe_ctx->stream && pipe_mall_type == SUBVP_PHANTOM
-			&& hubp->funcs->phantom_hubp_post_enable)
+	if (pipe_mall_type == SUBVP_PHANTOM && hubp->funcs->phantom_hubp_post_enable)
 		hubp->funcs->phantom_hubp_post_enable(hubp);
 }
 

drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c

@@ -916,8 +916,8 @@ enum dc_status dcn401_enable_stream_timing(
 	/* TODO enable stream if timing changed */
 	/* TODO unblank stream if DP */
 
-	if (pipe_ctx->stream && dc_state_get_pipe_subvp_type(context, pipe_ctx) == SUBVP_PHANTOM) {
-		if (pipe_ctx->stream_res.tg && pipe_ctx->stream_res.tg->funcs->phantom_crtc_post_enable)
+	if (dc_state_get_pipe_subvp_type(context, pipe_ctx) == SUBVP_PHANTOM) {
+		if (pipe_ctx->stream_res.tg->funcs->phantom_crtc_post_enable)
 			pipe_ctx->stream_res.tg->funcs->phantom_crtc_post_enable(pipe_ctx->stream_res.tg);
 	}
 

drivers/gpu/drm/amd/display/dc/link/accessories/link_dp_cts.c

@@ -853,7 +853,7 @@ bool dp_set_test_pattern(
 				CRTC_STATE_VACTIVE);
 
 		if (pipe_ctx->stream_res.tg->funcs->lock_doublebuffer_disable) {
-			if (pipe_ctx->stream && should_use_dmub_lock(pipe_ctx->stream->link)) {
+			if (should_use_dmub_lock(pipe_ctx->stream->link)) {
 				union dmub_hw_lock_flags hw_locks = { 0 };
 				struct dmub_hw_lock_inst_flags inst_flags = { 0 };