fs.h: Switch to using rtc_def.h

This file only needs the definition of 'struct rtc_time' and that is
found in <rtc_def.h>. Use that instead of pulling in rtc.h to pull in
rtc_def.h as rtc.h includes many other include files.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/fs.h b/include/fs.h
index 731aaa0..bec0211 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -5,7 +5,7 @@
 #ifndef _FS_H
 #define _FS_H
 
-#include <rtc.h>
+#include <rtc_def.h>
 
 struct cmd_tbl;