user_simtrace2: Fix uninitialized ifm->path

Let's memset the entire ifm before calling
osmo_libusb_open_claim_interface()

Fixes: CID#307510: Uninitialized scalar variable (UNINIT)
Change-Id: I2bd0dac76b6d028d10f12f3f58a2aee123ca8562
diff --git a/src/client/user_simtrace2.c b/src/client/user_simtrace2.c
index 29ab196..8dd3423 100644
--- a/src/client/user_simtrace2.c
+++ b/src/client/user_simtrace2.c
@@ -411,6 +411,7 @@
 	ci->priv = bc;
 	bc->cardem = ci;
 
+	memset(ifm, 0, sizeof(*ifm));
 	ifm->vendor = cfg->usb.vendor_id;
 	ifm->product = cfg->usb.product_id;
 	ifm->configuration = cfg->usb.config_id;