usb: gadget: net2272: Fix a memory leak in an error handling path in 'net2272_plat_probe()'

'dev' is allocated in 'net2272_probe_init()'. It must be freed in the error
handling path, as already done in the remove function (i.e.
'net2272_plat_remove()')

Fixes: 90fccb52

 ("usb: gadget: Gadget directory cleanup - group UDC drivers")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Felipe Balbi <balbi@kernel.org>