unix: add rtc defines and types

Change-Id: I280fc3b2cd3402c40f2840d152bac2fa288f48a0
Reviewed-on: https://go-review.googlesource.com/118661
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/linux/types.go

@@ -73,6 +73,7 @@ package unix
 #include <linux/genetlink.h>
 #include <linux/socket.h>
 #include <linux/hdreg.h>
+#include <linux/rtc.h>
 
 // abi/abi.h generated by mkall.go.
 #include "abi/abi.h"
@@ -1485,3 +1486,9 @@ const (
 	NFT_NG_INCREMENTAL                = C.NFT_NG_INCREMENTAL
 	NFT_NG_RANDOM                     = C.NFT_NG_RANDOM
 )
+
+type RTCTime C.struct_rtc_time
+
+type RTCWkAlrm C.struct_rtc_wkalrm
+
+type RTCPLLInfo C.struct_rtc_pll_info