N-type SOC need to swap some Serdes lines to make it work.

Without this fix N-type SOC devices like RTL8372N, RTL8383N and also the
4-port PHY RTL8224N, don't have a functional Serdes. Although the SOC
sees a link, there is no packet flow on both SFP-port nor RTL8224 ports.

Added helper functions to read/write to the RTL8224.
RTL8224 has the same register layout so we can use the same register
defines as for the main SOC.

rtl837x_regs.h

@@ -2,7 +2,7 @@
 #define _RTL837X_REGS_H_
 
 #define RTL837X_REG_CHIP_ID		0x0004
-#define RTL837X_REG_CHIP_INFO		0x000c
+#define RTL837X_REG_CHIP_INFO	0x000c
 #define RTL837X_REG_RESET		0x0024
 #define RESET_SOC_BIT			0
 #define RESET_NIC_BIT			2
@@ -36,7 +36,20 @@
 #define RTL837X_REG_SEC_COUNTER2 0x06f8
 // Used for counting seconds
 
-#define RTL837X_REG_SDS_MODES 0x7b20
+
+/*
+ * SDS
+ */
+#define RTL837X_SDS_INDACS_CMD			0x3F8
+#define RTL837X_SDS_INDACS_WRITE_DATA	0x400
+#define RTL837X_REG_SDS_MODES			0x7b20
+
+/*
+ * PHY
+ */
+ #define RTL837X_CFG_PHY_TX_POLARITY_SWAP	0xA94
+ #define RTL837X_CFG_PHY_MDI_REVERSE		0xA90
+
 /*
  * 5 Bits each give the state of the 2 SerDes of the RTL8372
  * Values are: