USB: Gadget: Reorder driver name assignment

Reorder the driver->name assignment so the 'iProduct' could be initialized
as well if both 'name' and 'iProduct' come as NULL by default.

Also, remove the misplaced 'extern' keyword.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>