usb: gadget: composite: fix NULL pointer when a non standard request is received

In case usb configuration is unknown (cdev->config == NULL), non standard
request should not be processed.
Remove also the cdev->config check below which will never happen.

This issue was seen using ums feature.

Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>

drivers/usb/gadget/composite.c

@@ -838,6 +838,9 @@ unknown:
 			ctrl->bRequestType, ctrl->bRequest,
 			w_value, w_index, w_length);
 
+		if (!cdev->config)
+			goto done;
+
 		/*
 		 * functions always handle their interfaces and endpoints...
 		 * punt other recipients (other, WUSB, ...) to the current
@@ -882,7 +885,7 @@ unknown:
 			value = f->setup(f, ctrl);
 		else {
 			c = cdev->config;
-			if (c && c->setup)
+			if (c->setup)
 				value = c->setup(c, ctrl);
 		}