drm/komeda: check for error-valued pointer

komeda_pipeline_get_state() may return an error-valued pointer, thus
check the pointer for negative or null value before dereferencing.

Fixes: 502932a03fce ("drm/komeda: Add the initial scaler support for CORE")
Signed-off-by: Amjad Ouled-Ameur <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/arm/display/komeda/komeda_pipeline_state.c

···
 	u32 avail_scalers;
 
 	pipe_st = komeda_pipeline_get_state(c->pipeline, state);
-	if (!pipe_st)
+	if (IS_ERR_OR_NULL(pipe_st))
 		return NULL;
 
 	avail_scalers = (pipe_st->active_comps & KOMEDA_PIPELINE_SCALERS) ^