can: ifi: Fix transmitter delay calculation

The CANFD transmitter delay calculation formula was updated in the
latest software drop from IFI and improves the behavior of the IFI
CANFD core during bitrate switching. Use the new formula to improve
stability of the CANFD operation.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Markus Marb <markus@marb.org>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>