staging: lirc: fix mismatch in mutex lock-unlock in imon_probe

If kzalloc failed for allocation of context, goto alloc_status_switch
leads to unlock of unacquired driver_lock. The patch moves
mutex_lock(&driver_lock) before allocation of context.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/lirc/lirc_imon.c

@@ -727,6 +727,9 @@ static int imon_probe(struct usb_interface *interface,
 	int i;
 	u16 vendor, product;
 
+	/* prevent races probing devices w/multiple interfaces */
+	mutex_lock(&driver_lock);
+
 	context = kzalloc(sizeof(struct imon_context), GFP_KERNEL);
 	if (!context) {
 		err("%s: kzalloc failed for context", __func__);
@@ -753,9 +756,6 @@ static int imon_probe(struct usb_interface *interface,
 	dev_dbg(dev, "%s: found iMON device (%04x:%04x, intf%d)\n",
 		__func__, vendor, product, ifnum);
 
-	/* prevent races probing devices w/multiple interfaces */
-	mutex_lock(&driver_lock);
-
 	/*
 	 * Scan the endpoint list and set:
 	 *	first input endpoint = IR endpoint