net: mctp: start tx queue on netdev open

We stop queues in ndo_stop, so they need to be restarted in ndo_open.
This allows us to resume tx after a link down/up cycle.

Suggested-by: Nitin Singh <nitsingh@nvidia.com>
Fixes: 0791c032 ("net: mctp: Add MCTP USB transport driver")
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20250526-dev-mctp-usb-v1-1-c7bd6cb75aa0@codeconstruct.com.au


Signed-off-by: Jakub Kicinski <kuba@kernel.org>