docs: ctucanfd: CTU CAN FD open-source IP core documentation.

docs: ctucanfd: CTU CAN FD open-source IP core documentation.

CTU CAN FD IP core documentation based on Martin Jeřábek's diploma theses
Open-source and Open-hardware CAN FD Protocol Support
https://dspace.cvut.cz/handle/10467/80366
.

Link: https://lore.kernel.org/all/692b965999ff6c272239df0fe1c76b68d02b134d.1647932262.git.pisa@cmp.felk.cvut.cz
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Martin Jerabek <martin.jerabek01@gmail.com>
Signed-off-by: Ondrej Ille <ondrej.ille@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>