cisco: enic: Fic an error handling path in 'vnic_dev_init_devcmd2()'

if 'ioread32()' returns 0xFFFFFFF, we have to go through the error
handling path as done everywhere else in this function.

Move the 'err_free_wq' label to better match its name and its location
and add a new label 'err_disable_wq'.
Update the code accordingly.

Fixes: 373fb087 ("enic: add devcmd2")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>