can: esd_usb2: fix memory leak

can: esd_usb2: fix memory leak

In esd_usb2_setup_rx_urbs() MAX_RX_URBS coherent buffers are allocated
and there is nothing, that frees them:

1) In callback function the urb is resubmitted and that's all
2) In disconnect function urbs are simply killed, but URB_FREE_BUFFER
   is not set (see esd_usb2_setup_rx_urbs) and this flag cannot be used
   with coherent buffers.

So, all allocated buffers should be freed with usb_free_coherent()
explicitly.

Side note: This code looks like a copy-paste of other can drivers. The
same patch was applied to mcba_usb driver and it works nice with real
hardware. There is no change in functionality, only clean-up code for
coherent buffers.

Fixes: 96d8e90382dc ("can: Add driver for esd CAN-USB/2 device")
Link: https://lore.kernel.org/r/b31b096926dcb35998ad0271aac4b51770ca7cc8.1627404470.git.paskripkin@gmail.com
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>