can: dev: alloc_candev_mqs(): add missing default CAN capabilities

The idea behind series 6c1f5146 ("Merge patch series "can: raw: better
approach to instantly reject unsupported CAN frames"") is to set the
capabilities of a CAN device (CAN-CC, CAN-FD, CAN-XL, and listen only) [1]
and, based on these capabilities, reject unsupported CAN frames in the
CAN-RAW protocol [2].

This works perfectly for CAN devices configured in CAN-FD or CAN-XL mode.
CAN devices with static CAN control modes define their capabilities via
can_set_static_ctrlmode() -> can_set_cap_info(). CAN devices configured by
the user space for CAN-FD or CAN-XL set their capabilities via
can_changelink() -> can_ctrlmode_changelink() -> can_set_cap_info().

However, in commit 166e8732 ("can: propagate CAN device capabilities
via ml_priv"), the capabilities of CAN devices are not initialized.
This results in CAN-RAW rejecting all CAN frames on devices directly
after ifup if the user space has not changed the CAN control mode.

Fix this problem by setting the default capabilities to CAN-CC in
alloc_candev_mqs() as soon as the CAN specific ml_priv is allocated.

[1] commit 166e8732 ("can: propagate CAN device capabilities via ml_priv")
[2] commit faba5860 ("can: raw: instantly reject disabled CAN frames")

Fixes: 166e8732 ("can: propagate CAN device capabilities via ml_priv")
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260116-can_add_missing_set_caps-v1-1-7525126d8b20@pengutronix.de


[mkl: fix typo in subject]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>