drm/amd/display: Fix memory leak reported by coverity

Free memory allocated if any of the previous allocations failed.

>>>     CID 1487129:  Resource leaks  (RESOURCE_LEAK)
>>>     Variable "vpg" going out of scope leaks the storage it points to.

Addresses-Coverity-ID: 1487129: ("Resource leaks")
Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Anson Jacob <Anson.Jacob@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn303/dcn303_resource.c

@@ -510,8 +510,12 @@ static struct stream_encoder *dcn303_stream_encoder_create(enum engine_id eng_id
 	vpg = dcn303_vpg_create(ctx, vpg_inst);
 	afmt = dcn303_afmt_create(ctx, afmt_inst);
 
-	if (!enc1 || !vpg || !afmt)
+	if (!enc1 || !vpg || !afmt) {
+		kfree(enc1);
+		kfree(vpg);
+		kfree(afmt);
 		return NULL;
+	}
 
 	dcn30_dio_stream_encoder_construct(enc1, ctx, ctx->dc_bios, eng_id, vpg, afmt, &stream_enc_regs[eng_id],
 			&se_shift, &se_mask);