disp: msm: sde: add check to avoid NULL WB output fb

Change the debug message to error during the writeback
encoder validate for wb output buffer. The output buffer
can be NULL only during disable frame and all other frames
need to have a valid output buffer.

Change-Id: I4d6fecfeaf863e56fe25e17ab1200849003b3309
Signed-off-by: Veera Sundaram Sankaran <quic_veeras@quicinc.com>

msm/sde/sde_encoder_phys_wb.c

@@ -1024,8 +1024,8 @@ static int sde_encoder_phys_wb_atomic_check(struct sde_encoder_phys *phys_enc,
 	/* bypass check if commit with no framebuffer */
 	fb = sde_wb_connector_state_get_output_fb(conn_state);
 	if (!fb) {
-		SDE_DEBUG("[enc:%d wb:%d] no out fb\n", DRMID(phys_enc->parent), WBID(wb_enc));
-		return 0;
+		SDE_ERROR("[enc:%d wb:%d] no out fb\n", DRMID(phys_enc->parent), WBID(wb_enc));
+		return -EINVAL;
 	}
 
 	fmt = sde_get_sde_format_ext(fb->format->format, fb->modifier);