jbd.h: bitfields should be unsigned

bitfields should be unsigned.

This fixes sparse noise:
  error: dubious one-bit signed bitfield
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Jan Kara <jack@ucw.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/jbd.h

@@ -556,7 +556,7 @@ struct transaction_s
 	 * This transaction is being forced and some process is
 	 * waiting for it to finish.
 	 */
-	int t_synchronous_commit:1;
+	unsigned int t_synchronous_commit:1;
 };
 
 /**