jbd/jbd2: relocate bit_spinlock header to jbd_common

The bit_spinlock functions are only used for the jbd_lock_bh_state
functions (and friends) in jbd_common.h and are not directly used
by either of jbd.h or jbd2.h content.

The jbd_common file is new as of commit 446066724c ("jdb/jbd2: factor
out common functions from the jbd[2] header files") but common
(and isolated) headers were not considered for factoring at that time.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

include/linux/jbd_common.h

@@ -1,6 +1,8 @@
 #ifndef _LINUX_JBD_STATE_H
 #define _LINUX_JBD_STATE_H
 
+#include <linux/bit_spinlock.h>
+
 static inline struct buffer_head *jh2bh(struct journal_head *jh)
 {
 	return jh->b_bh;