xf86drm: continue with next device if drmProcessUsbDevice fails

Analogous to previous commit (and the rest of the codebase), simply
discard the device if we cannot parse it.

Fixes: f8484ccbd12 ("xf86drm: Add USB support")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
diff --git a/xf86drm.c b/xf86drm.c
index f306c9b..6ea0112 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -3989,7 +3989,7 @@
             ret = drmProcessUsbDevice(&device, node, node_type, maj, min,
                                       devices != NULL, flags);
             if (ret)
-                goto free_devices;
+                continue;
 
             break;