headers: remove sched.h from interrupt.h

After m68k's task_thread_info() doesn't refer to current,
it's possible to remove sched.h from interrupt.h and not break m68k!
Many thanks to Heiko Carstens for allowing this.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 2755a3b..eae56fd 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -9,6 +9,7 @@
  */
 #include <linux/debugobjects.h>
 #include <linux/interrupt.h>
+#include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 #include <linux/hash.h>