gve: Fix an error handling path in 'gve_probe()'

If the 'register_netdev() call fails, we must release the resources
allocated by the previous 'gve_init_priv()' call, as already done in the
remove function.

Add a new label and the missing 'gve_teardown_priv_resources()' in the
error handling path.

Fixes: 893ce44d ("gve: Add basic driver framework for Compute Engine Virtual NIC")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>