lguest: Use explicit includes rateher than indirect

explicitly use ktime.h include
explicitly use hrtimer.h include
explicitly use sched.h include

This patch adds headers explicitly to lguest sources file,
to avoid depending on them being included somewhere else.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index a87fca6..85d42d3 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -6,6 +6,7 @@
 #include <linux/uaccess.h>
 #include <linux/miscdevice.h>
 #include <linux/fs.h>
+#include <linux/sched.h>
 #include "lg.h"
 
 /*L:055 When something happens, the Waker process needs a way to stop the