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/char/ser_a2232.c b/drivers/char/ser_a2232.c
index 33a2b53..9610861 100644
--- a/drivers/char/ser_a2232.c
+++ b/drivers/char/ser_a2232.c
@@ -89,6 +89,7 @@
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/sched.h>
 #include <linux/tty.h>
 
 #include <asm/setup.h>