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/wireless/b43legacy/main.c b/drivers/net/wireless/b43legacy/main.c
index 1d9223b..4b60148 100644
--- a/drivers/net/wireless/b43legacy/main.c
+++ b/drivers/net/wireless/b43legacy/main.c
@@ -37,6 +37,7 @@
 #include <linux/firmware.h>
 #include <linux/wireless.h>
 #include <linux/workqueue.h>
+#include <linux/sched.h>
 #include <linux/skbuff.h>
 #include <linux/dma-mapping.h>
 #include <net/dst.h>