igb: correct register comments

Signed-off-by: NCao jin <caoj.fnst@cn.fujitsu.com>
Tested-by: NAaron Brown <aaron.f.brown@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/e1000_regs.h

@@ -320,7 +320,7 @@
 #define E1000_VT_CTL   0x0581C  /* VMDq Control - RW */
 #define E1000_WUC      0x05800  /* Wakeup Control - RW */
 #define E1000_WUFC     0x05808  /* Wakeup Filter Control - RW */
-#define E1000_WUS      0x05810  /* Wakeup Status - RO */
+#define E1000_WUS      0x05810  /* Wakeup Status - R/W1C */
 #define E1000_MANC     0x05820  /* Management Control - RW */
 #define E1000_IPAV     0x05838  /* IP Address Valid - RW */
 #define E1000_WUPL     0x05900  /* Wakeup Packet Length - RW */