can: mcp251xfd: revert "can: mcp251xfd: add BQL support"

can: mcp251xfd: revert "can: mcp251xfd: add BQL support"

In the following 4 patches

| e4b619d9fe49 can: dev: can_rx_offload_get_echo_skb(): extend to return can frame length
| ab34ba813009 can: dev: can_get_echo_skb(): extend to return can frame length
| 5da84ca5b2da can: dev: can_put_echo_skb(): extend to handle frame_len
| ddec13273d24 can: dev: extend struct can_skb_priv to hold CAN frame length

the CAN echo SKB support was extended to hold the CAN frame
length (which is the length of the CAN frame on the wire). It is meant
as a helper for BQL support, to avoid the re-calculation of the frame
length before sending it and on TX-completion.

However if the CAN frame is send without the request to be looped back
the SKB is discarded in can_put_echo_skb() and the subsequent
can_get_echo_skb() and can_rx_offload_get_echo_skb() return 0 for the
CAN frame length. This results in BQL stalling the TX queue after a
few packages.

Until the BQL helpers can_get_echo_skb() and
can_rx_offload_get_echo_skb() are fixed, revert the BQL support for
the mcp251xfd driver.

This reverts commit b8dd408e905a54d1d97e285d21c4de4a770849cc.

Fixes: b8dd408e905a ("can: mcp251xfd: add BQL support")
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Thomas Kopp <thomas.kopp@microchip.com>
Link: https://lore.kernel.org/r/20210228083347.28580-1-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>