Add two helpers to retrieve the data length from CAN sk_buffs and prepare
the length information to be a uint16 value for the CAN XL support.
Acked-by: NVincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: NOliver Hartkopp <socketcan@hartkopp.net>
Link: https://lore.kernel.org/all/20220912170725.120748-3-socketcan@hartkopp.netSigned-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>