can: bittiming: replace CAN units with the generic ones from linux/units.h

In [1], we introduced a set of units in linux/can/bittiming.h. Since
then, generic SI prefixes were added to linux/units.h in [2]. Those
new prefixes can perfectly replace CAN specific ones.

This patch replaces all occurrences of the CAN units with their
corresponding prefix (from linux/units) and the unit (as a comment)
according to below table.

 CAN units	SI metric prefix (from linux/units) + unit (as a comment)
 ------------------------------------------------------------------------
 CAN_KBPS	KILO /* BPS */
 CAN_MBPS	MEGA /* BPS */
 CAM_MHZ	MEGA /* Hz */

The definition are then removed from linux/can/bittiming.h

[1] commit 1d775076 ("can: bittiming: add CAN_KBPS, CAN_MBPS and
CAN_MHZ macros")

[2] commit 26471d4a ("units: Add SI metric prefix definitions")

Link: https://lore.kernel.org/all/20211124014536.782550-1-mailhol.vincent@wanadoo.fr


Suggested-by: Jimmy Assarsson <extja@kvaser.com>
Suggested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>