i2c-pxa2xx: check timeout correctly

timeout here maybe 0 if the event occured and a task with a higher
priority stole the cpu and we were sleeping longer than the timeout
value we specified.
In case of a real timeout I changed the error code to I2C_RETRY so we
retry the transfer.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

drivers/i2c/busses/i2c-pxa.c

@@ -770,8 +770,10 @@ static int i2c_pxa_do_xfer(struct pxa_i2c *i2c, struct i2c_msg *msg, int num)
 	 */
 	ret = i2c->msg_idx;
 
-	if (timeout == 0)
+	if (!timeout && i2c->msg_num) {
 		i2c_pxa_scream_blue_murder(i2c, "timeout");
+		ret = I2C_RETRY;
+	}
 
  out:
 	return ret;