net: dcb: add new apptrust attribute

Add new apptrust extension attributes to the 8021Qaz APP managed object.

Two new attributes, DCB_ATTR_DCB_APP_TRUST_TABLE and
DCB_ATTR_DCB_APP_TRUST, has been added. Trusted selectors are passed in
the nested attribute DCB_ATTR_DCB_APP_TRUST, in order of precedence.

The new attributes are meant to allow drivers, whose hw supports the
notion of trust, to be able to set whether a particular app selector is
trusted - and in which order.

Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>