Introduce global error variable, check during config execution

rtl837x_common.h

@@ -42,6 +42,11 @@ extern __xdata uint8_t sbuf[SBUF_SIZE];
 // Size of the flash buffer used for writing to flash, must be a multiple of the flash page size (0x100)
 #define FLASH_BUF_SIZE 512
 
+// Errors for commands
+#define ERR_OK			0
+#define ERR_TOO_MANY_ARGUMENTS	1
+#define ERR_CMD_TOO_LONG	2
+
 // For RX data, a propriatary RTL FRAME is inserted. Instead of 0x0800 for IPv4,
 // the RTL_FRAME_TAG_ID is used as part of an 8-byte tag. When VLAN is activated,
 // the VLAN tag is inserted after the RTL tag