headers: Fix build after <linux/sched.h> removal

Commit d43c36dc6b ("headers: remove
sched.h from interrupt.h") left some build errors in some configurations
due to drivers having depended on getting header files "accidentally".

Signed-off-by: Ingo Molnar <mingo@elte.hu>
[ Combined several one-liners from Ingo into one single patch  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/genrtc.c

@@ -43,6 +43,7 @@
 #define RTC_VERSION	"1.07"
 
 #include <linux/module.h>
+#include <linux/sched.h>
 #include <linux/errno.h>
 #include <linux/miscdevice.h>
 #include <linux/fcntl.h>