net/fm10k/base: improve re-map queues handle

net/fm10k/base: improve re-map queues handle

Avoid potential FUM fault errors on a VF when updating MAC address
and VLAN information. Only use the register flow when the mailbox is
disconnected, by checking if the enqueue_tx returns
FM10K_MBX_ERR_NO_MBX. If the mailbox message can be sent, there is no
reason to bother with the register writes which are only intended to
be used during VF driver initialization.

Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>