usb: gadget: Remove set but not used variable 'opts' in msg_do_config

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/usb/gadget/legacy/mass_storage.c: In function msg_do_config:
drivers/usb/gadget/legacy/mass_storage.c:108:19: warning: variable opts set but not used [-Wunused-but-set-variable]

It is not used since commit f78bbcae ("usb: f_mass_storage:
test whether thread is running before starting another")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Link: https://lore.kernel.org/r/1570610434-68293-3-git-send-email-zhengbin13@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/legacy/mass_storage.c

@@ -105,7 +105,6 @@ FSG_MODULE_PARAMETERS(/* no prefix */, mod_data);
 
 static int msg_do_config(struct usb_configuration *c)
 {
-	struct fsg_opts *opts;
 	int ret;
 
 	if (gadget_is_otg(c->cdev->gadget)) {
@@ -113,8 +112,6 @@ static int msg_do_config(struct usb_configuration *c)
 		c->bmAttributes |= USB_CONFIG_ATT_WAKEUP;
 	}
 
-	opts = fsg_opts_from_func_inst(fi_msg);
-
 	f_msg = usb_get_function(fi_msg);
 	if (IS_ERR(f_msg))
 		return PTR_ERR(f_msg);