wil6210: P2P_DEVICE virtual interface support

Added support for the P2P_DEVICE virtual interface. This interface
is intended for P2P management operations such as discovery and
GO negotiation. Normally it is implemented by drivers to allow
a separate interface for P2P management with its own MAC address,
but for 11ad drivers it is needed to support P2P search, since it
cannot otherwise be separated from normal scan.

Since we only support a single interface/MAC address, we can't
easily separate between primary and P2P_DEVICE interfaces.
For example when a management packet arrives we can't tell for
which interface it is intended. To work around this, we store
a pointer to the interface where the last "radio operation" was
triggered such as scan or remain on channel, and we forward
management packets and scan results to this interface.

Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>