igb: When GbE link up, wait for Remote receiver status condition

I210 device IPv6 autoconf test sometimes fails,
because DAD NS for link-local is not transmitted.
This packet is silently dropped.
This problem is seen only GbE environment.

igb_watchdog_task link up detection continues to the following process.
The following cases are observed:
1.PHY 1000BASE-T Status Register Remote receiver status bit is NG.
(NG status becomes OK after about 200 - 700ms)
2.In this case, the transfer packet is silently dropped.

1000BASE-T Status register
[Expected]: 0x3800 or 0x7800
[problem occurred]: 0x2800 or 0x6800
Frequency of occurrence: approx 1/10 - 1/40 observed

In order to avoid this problem,
wait until 1000BASE-T Status register "Remote receiver status OK"

After applying this patch, at least 400 runs succeed with no problems.

Signed-off-by: Takuma Ueba <t.ueba11@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>