can: ifi: Update timing configuration code

The updated documentation regarding the IFI CANFD core from April 2016
adds more details regarding the timing calculation. There is no longer
any distinction in the timing calculation between CANFD and CAN2.0, but
instead there are two timing modes -- 4_12_6_6 and 7_9_8_8 -- where the
numbers mean the width in bits of the SJW/Prescaler/TimeA/TimeB fields.
The code uses 7_9_8_8 mode, which allows more fine-grained control over
the timing.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>