headers: smp_lock.h redux

* Remove smp_lock.h from files which don't need it (including some headers!)
* Add smp_lock.h to files which do need it
* Make smp_lock.h include conditional in hardirq.h
  It's needed only for one kernel_locked() usage which is under CONFIG_PREEMPT

  This will make hardirq.h inclusion cheaper for every PREEMPT=n config
  (which includes allmodconfig/allyesconfig, BTW)

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/serial167.c b/drivers/char/serial167.c
index f1f24f0..51e7a46 100644
--- a/drivers/char/serial167.c
+++ b/drivers/char/serial167.c
@@ -52,6 +52,7 @@
 #include <linux/interrupt.h>
 #include <linux/serial.h>
 #include <linux/serialP.h>
+#include <linux/smp_lock.h>
 #include <linux/string.h>
 #include <linux/fcntl.h>
 #include <linux/ptrace.h>