Delete rtcdate, which is a left-over from an old lab (thanks Harry Porter)

kernel/date.h

@@ -1,8 +0,0 @@
-struct rtcdate {
-  uint second;
-  uint minute;
-  uint hour;
-  uint day;
-  uint month;
-  uint year;
-};

kernel/sysproc.c

@@ -1,7 +1,6 @@
 #include "types.h"
 #include "riscv.h"
 #include "defs.h"
-#include "date.h"
 #include "param.h"
 #include "memlayout.h"
 #include "spinlock.h"

user/user.h

@@ -1,5 +1,4 @@
 struct stat;
-struct rtcdate;
 
 // system calls
 int fork(void);