Fallout from "Remove fs.h from mm.h" patch

While I was busy compile-testing my patch, ENOSYS sneaked into pm.h
leading to some compile-breakages mostly on ia64 and some mips configs.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pm.h

@@ -25,6 +25,7 @@
 
 #include <linux/list.h>
 #include <asm/atomic.h>
+#include <asm/errno.h>
 
 /*
  * Power management requests... these are passed to pm_send_all() and friends.