jbd2: drop declaration of journal_sync_buffer()

The journal_sync_buffer() function was never carried over from jbd to
jbd2.  So get rid of the vestigal declaration of this (non-existent)
function.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/jbd2/journal.c

@@ -66,9 +66,6 @@ EXPORT_SYMBOL(jbd2_journal_get_undo_access);
 EXPORT_SYMBOL(jbd2_journal_set_triggers);
 EXPORT_SYMBOL(jbd2_journal_dirty_metadata);
 EXPORT_SYMBOL(jbd2_journal_forget);
-#if 0
-EXPORT_SYMBOL(journal_sync_buffer);
-#endif
 EXPORT_SYMBOL(jbd2_journal_flush);
 EXPORT_SYMBOL(jbd2_journal_revoke);