can: netlink: can_changelink(): rename tdc_mask into fd_tdc_flag_provided

The only purpose of the tdc_mask variable is to check whether or not
any tdc flags (CAN_CTRLMODE_TDC_{AUTO,MANUAL}) were provided. At this
point, the actual value of the flags do no matter any more because
these can be deduced from some other information.

Rename the tdc_mask variable into fd_tdc_flag_provided to make this
more explicit. Note that the fd_ prefix is added in preparation of the
introduction of CAN XL.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://patch.msgid.link/20241112165118.586613-12-mailhol.vincent@wanadoo.fr


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