pibridge-serdev: add error and info messages at startup

If pibridge_probe() fails for any other reason than failed memory allocation there is no hint for this in the kernel log file (also the caller of pibridge_probe() does print an according error message. So add some error messages directly in this function and also print an info message in case that probing was successful.

Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com