DM: vrtc code cleanup

- Move the variable local_time from main.c to rtc.c
- Change vrtc_init to return int instead of pointer to vrtc. We do
  track vrtc in struct vmctx.

Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>

devicemodel/include/rtc.h

@@ -36,7 +36,8 @@
 struct vrtc;
 struct vmctx;
 
-struct vrtc  *vrtc_init(struct vmctx *ctx, int local_time);
+int vrtc_init(struct vmctx *ctx);
+void vrtc_enable_localtime(int l_time);
 void vrtc_deinit(struct vmctx *ctx);
 void vrtc_reset(struct vrtc *vrtc);
 time_t vrtc_get_time(struct vrtc *vrtc);