tty: xuartps: Print warning in clock notifier

Print a warning if the clock notifier rejects a clock frequency change
to facilitate debugging (see:
http://thread.gmane.org/gmane.linux.ports.arm.kernel/304329/focus=304379)

Signed-off-by: Soren Brinkmann <[e-mail]>
Tested-by: Michal Simek <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/xilinx_uartps.c

···
 		 * frequency.
 		 */
 		if (!xuartps_calc_baud_divs(ndata->new_rate, xuartps->baud,
-					&bdiv, &cd, &div8))
+					&bdiv, &cd, &div8)) {
+			dev_warn(port->dev, "clock rate change rejected\n");
 			return NOTIFY_BAD;
+		}
 
 		spin_lock_irqsave(&xuartps->port->lock, flags);