wil6210: add support for pci linkdown recovery

Some platforms can notify on pci linkdown events.
Add pci linkdown recovery flow, invoked upon pci linkdown
notification.
A new wil6210 status flag is added, wil_status_pci_linkdown, to
prevent pci suspend / resume until the recovery is completed.
After the pci link is recovered in the platform pci recovery
callback the device is being reset and the the interface and AP
mode states are restored.

Change-Id: I6e0f434d52704120c683c51fb4d664eccca16f01
Signed-off-by: Maya Erez <merez@codeaurora.org>
[liord@codeaurora.org: fix merge conflicts]
Signed-off-by: Lior David <liord@codeaurora.org>