can-calc-bit-timing: calculate bit timings for all known controllers by default

can-calc-bit-timing: calculate bit timings for all known controllers by default

When testing or improving the bit timing algorithm, you're probably
interested in the values of all can controllers. Further you might not
know the all reference clocks of the controllers.

This patch add a "ref_clock" member to the "struct can_bittiming_const"
that holds the reference clock of the controller in Hz.

By default now the bit timing is calculated for all known can
controllers with the default ref_clock defined in "can_bittiming_const".

It's still possible to overwrite the ref clock with the command line
option "-c".

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