net: hibmcge: Add support for mac link exception handling feature

If the rate changed frequently, the PHY link ok,
but the MAC link maybe fails.
As a result, the network port is unavailable.

According to the documents of the chip,
core_reset needs to do to fix the fault.

In hw_adjus_link(), the core_reset is added to try to
ensure that MAC link status is normal.
In addition, MAC link failure detection is added.
If the MAC link fails after core_reset, driver invokes
the phy_stop() and phy_start() to re-link.

Due to phydev->lock, re-link cannot be triggered
in adjust_link(). Therefore, this operation
is invoked in a scheduled task.

Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>