realtek: dsa: rtl839x: share the first L3 row of the PIE

The ethernet driver is about to tell a frame that a tc rule sent to the
CPU from one that an L3 rule sent there, and only the PIE row in the
CPU tag tells them apart. Move RTL839X_PIE_L3_FIRST to a new shared
header, include/linux/soc/realtek/otto_common.h, and derive the number
of L3 rows from it. Both values stay as they were, 640 and 512.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Gennaro Cimmino <gcimmino@rayonra.net>
Link: https://github.com/openwrt/openwrt/pull/25919
Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>

target/linux/realtek/files-6.18/drivers/net/dsa/rtl83xx/pie.h

@@ -2,6 +2,7 @@
 #ifndef _OTTO_PIE_H
 #define _OTTO_PIE_H
 
+#include <linux/soc/realtek/otto_common.h>
 #include <linux/types.h>
 
 /* PIE actions */
@@ -19,8 +20,7 @@
  * ingress comes before routing.
  */
 #define RTL839X_PIE_CUTLINE	9
-#define RTL839X_PIE_L3_RULES	(4 * PIE_BLOCK_SIZE)
-#define RTL839X_PIE_L3_FIRST	(RTL839X_PIE_CUTLINE * PIE_BLOCK_SIZE - RTL839X_PIE_L3_RULES)
+#define RTL839X_PIE_L3_RULES	(RTL839X_PIE_CUTLINE * PIE_BLOCK_SIZE - RTL839X_PIE_L3_FIRST)
 
 struct pie_rule;
 struct otto_dsa_priv;

target/linux/realtek/files-6.18/include/linux/soc/realtek/otto_common.h

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _OTTO_COMMON_H
+#define _OTTO_COMMON_H
+
+#define RTL839X_PIE_L3_FIRST	640
+
+#endif /* _OTTO_COMMON_H */