jbd2: Fix CONFIG_JBD_DEBUG ifdef to be CONFIG_JBD2_DEBUG

When the JBD code was forked to create the new JBD2 code base, the
references to CONFIG_JBD_DEBUG where never changed to
CONFIG_JBD2_DEBUG.  This patch fixes that.

Signed-off-by: Jose R. Santos <jrs@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/include/linux/ext4_fs_sb.h b/include/linux/ext4_fs_sb.h
index 2347557..0f7dc159 100644
--- a/include/linux/ext4_fs_sb.h
+++ b/include/linux/ext4_fs_sb.h
@@ -73,7 +73,7 @@
 	struct list_head s_orphan;
 	unsigned long s_commit_interval;
 	struct block_device *journal_bdev;
-#ifdef CONFIG_JBD_DEBUG
+#ifdef CONFIG_JBD2_DEBUG
 	struct timer_list turn_ro_timer;	/* For turning read-only (crash simulation) */
 	wait_queue_head_t ro_wait_queue;	/* For people waiting for the fs to go read-only */
 #endif