can: kvaser_pciefd: Use TX FIFO size read from CAN controller

Use the TX FIFO size read from CAN controller register, instead of using
hard coded value.

Signed-off-by: Jimmy Assarsson <extja@kvaser.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/20230529134248.752036-15-extja@kvaser.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>