drm/i915/display: Avoid divide by zero

skl_crtc_allocate_plane_ddb allow iter.data_rate to be zero
which could cause divide by zero in skl_allocate_plane_ddb,
check against that.

Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Link: https://lore.kernel.org/r/20250905104626.1274147-3-juhapekka.heikkila@gmail.com

Author: juhapekka

drivers/gpu/drm/i915/display/skl_watermark.c

@@ -1388,7 +1388,7 @@ skl_allocate_plane_ddb(struct skl_plane_ddb_iter *iter,
 {
 	u16 size, extra = 0;
 
-	if (data_rate) {
+	if (data_rate && iter->data_rate) {
 		extra = min_t(u16, iter->size,
 			      DIV64_U64_ROUND_UP(iter->size * data_rate,
 						 iter->data_rate));