r8152: Run the unload routine if we have errors during probe

The rtl8152_probe() function lacks a call to the chip-specific
unload() routine when it sees an error in probe. Add it in to match
the cleanup code in rtl8152_disconnect().

Fixes: ac718b69

 ("net/usb: new driver for RTL8152")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>