usb: gadget: free opts struct on error recovery

Fix memory leaks introduced in commits:

40d133d7f542616cf9538508a372306e626a16e9
usb: gadget: f_ncm: convert to new function interface with backward compatibility

fee562a6450b7806f1fbbe1469a67b5395b5c10a
usb: gadget: f_ecm: convert to new function interface with backward compatibility

fcbdf12ebef73a6069e2a1aada1e546fb578a4aa
usb: gadget: f_phonet: convert to new function interface with backward compatibility

b29002a157940752dfed2c488b2011f63f007d71
usb: gadget: f_eem: convert to new function interface with backward compatibility

8cedba7c73af1369599b1111639cfeb66fe13aaa
usb: gadget: f_subset: convert to new function interface with backward compatibility

f466c6353819326873fa48a02c6f2d7c903240d6
usb: gadget: f_rndis: convert to new function interface with backward compatibility

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>