nl80211: allow user-space to set address for P2P_DEVICE

nl80211: allow user-space to set address for P2P_DEVICE

As per email discussion Jouni Malinen pointed out that:

"P2P message exchanges can be executed on the current operating channel
of any operation (both P2P and non-P2P station). These can be on 5 GHz
and even on 60 GHz (so yes, you _can_ do GO Negotiation on 60 GHz).

As an example, it would be possible to receive a GO Negotiation Request
frame on a 5 GHz only radio and then to complete GO Negotiation on that
band. This can happen both when connected to a P2P group (through client
discoverability mechanism) and when connected to a legacy AP (assuming
the station receive Probe Request frame from full scan in the beginning
of P2P device discovery)."

This means that P2P messages can be sent over different radio devices.
However, these should use the same P2P device address so it should be
able to provision this from user-space. This patch adds a parameter for
this to struct vif_params which should only be used during creation of
the P2P device interface.

Cc: Jouni Malinen <j@w1.fi>
Cc: Greg Goldman <ggoldman@broadcom.com>
Cc: Jithu Jance <jithu@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
[add error checking]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>