can: kvaser_usb: Add helper functions to convert device timestamp into ktime

can: kvaser_usb: Add helper functions to convert device timestamp into ktime

Add helper function kvaser_usb_ticks_to_ktime() that converts from
device ticks to ktime.
And kvaser_usb_timestamp{48,64}_to_ktime() that converts from device
48-bit or 64-bit timestamp, to ktime.

Signed-off-by: Jimmy Assarsson <extja@kvaser.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/20240701154936.92633-2-extja@kvaser.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>