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/drivers/net/hamradio/hdlcdrv.c b/drivers/net/hamradio/hdlcdrv.c
index 0013c40..91c5790 100644
--- a/drivers/net/hamradio/hdlcdrv.c
+++ b/drivers/net/hamradio/hdlcdrv.c
@@ -42,6 +42,7 @@
 
 /*****************************************************************************/
 
+#include <linux/capability.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/net.h>