drm/i915/drm: Fix comment for YCbCr20 qp table declaration

Fix comment for YCbCr420 qp table declaration of max value
where the min value is 4 and the max value is 12/15/18
depending on bpc.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230705051502.2568245-3-suraj.kandpal@intel.com

Author: surajk8

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

@@ -17,13 +17,17 @@
 /* from BPP 6 to 36 in steps of 0.5 */
 #define RC_RANGE_QP444_12BPC_MAX_NUM_BPP	61
 
-/* from BPP 6 to 24 in steps of 0.5 */
+/* For YCbCr420 the bits_per_pixel sent in PPS params
+ * is double the target bpp. The below values represent
+ * the target bpp.
+ */
+/* from BPP 4 to 12 in steps of 0.5 */
 #define RC_RANGE_QP420_8BPC_MAX_NUM_BPP		17
 
-/* from BPP 6 to 30 in steps of 0.5 */
+/* from BPP 4 to 15 in steps of 0.5 */
 #define RC_RANGE_QP420_10BPC_MAX_NUM_BPP	23
 
-/* from BPP 6 to 36 in steps of 0.5 */
+/* from BPP 4 to 18 in steps of 0.5 */
 #define RC_RANGE_QP420_12BPC_MAX_NUM_BPP	29
 
 /*