net/ixgbevf: add full link status check option

net/ixgbevf: add full link status check option

To get the VF's link status by calling 'rte_eth_link_get_nowait()', the
VF not only check PF's physical link status, but also check the mailbox
running status. And mailbox checking will generate mailbox interrupt in
PF, it will be worse if many VFs are running in the system, the PF will
have to handle many interrrupts.

Normally, checking the PF's physical link status is enough for nowait.
For different scenarios, adding an 'pflink_fullchk' option to control
whether to check the link fully or not.

Fixes: 91546fb62e67 ("net/ixgbevf: fix link state")
Cc: stable@dpdk.org
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Acked-by: Scott Daniels <daniels@research.att.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>