[SERIAL] returning proper error from serial core driver

Fix the issue of returning 0 even in case of error from uart_set_info
function.  Now it returns the error EBUSY when it can not set new port.
Signed-off-by: NRam Gupta <r.gupta@astronautics.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

drivers/serial/serial_core.c

@@ -792,6 +792,7 @@ static int uart_set_info(struct uart_state *state,
 			 * We failed anyway.
 			 */
 			retval = -EBUSY;
+			goto exit;  // Added to return the correct error -Ram Gupta
 		}
 	}