can: pcan_usb: pcan_usb_fd_send_cmd(): silence compiler warning about uninitialized var

This patch silences the compiler warning:

drivers/net/can/usb/peak_usb/pcan_usb_fd.c: In function 'pcan_usb_fd_send_cmd':
drivers/net/can/usb/peak_usb/pcan_usb_fd.c:185:6: warning: 'err' may be used uninitialized in this function [-Wuninitialized]

by initialising the variable as 0.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/peak_usb/pcan_usb_fd.c

@@ -182,7 +182,7 @@ static inline void *pcan_usb_fd_cmd_buffer(struct peak_usb_device *dev)
 static int pcan_usb_fd_send_cmd(struct peak_usb_device *dev, void *cmd_tail)
 {
 	void *cmd_head = pcan_usb_fd_cmd_buffer(dev);
-	int err;
+	int err = 0;
 	u8 *packet_ptr;
 	int i, n = 1, packet_len;
 	ptrdiff_t cmd_len;