net/i40e: fix DCB configuration

net/i40e: fix DCB configuration

Removing stopping LLDP in firmware is a workaround for a
known errata which can cause Rx hang. But the changing will
cause DCB configuration fails. That is because when LLDP is
enabled, the return value of i40e_init_dcb is success. But
following check just considered the case when LLDP agent
is disabled.
This patch fixes this issue.

Fixes: fcbd40d4327b ("net/i40e: fix Rx hang when disable LLDP")
Signed-off-by: Jingjing Wu <jingjing.wu@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>