mlxsw: spectrum_switchdev: Add support for locked FDB notifications

In Spectrum, learning happens in parallel to the security checks.
Therefore, regardless of the result of the security checks, a learning
notification will be generated by the device and polled later on by the
driver.

Currently, the driver reacts to learning notifications by programming
corresponding FDB entries to the device. When a port is locked (i.e.,
has security checks enabled), this can no longer happen, as otherwise
any host will blindly gain authorization.

Instead, notify the learned entry as a locked entry to the bridge driver
that will in turn notify it to user space, in case MAB is enabled. User
space can then decide to authorize the host by clearing the "locked"
flag, which will cause the entry to be programmed to the device.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>