wpa_supplicant: Add a configuration file for the P2P_DEVICE parameters

wpa_supplicant: Add a configuration file for the P2P_DEVICE parameters

Add an option to specify a configuration file that can be used to hold
the P2P_DEVICE configuration parameters. If this option is not used, the
P2P_DEVICE configuration parameters will be read from interface
configuration file.

Note that it is advised to use this option in some cases such as:

If a P2P_DEVICE is supported by the driver, the wpa_supplicant creates a
dedicated P2P Device interface, where the configuration file used for
the main interface is used. As a consequence, if the configuration file
includes network definition etc., the wpa_supplicant will try to perform
station specific flows on the P2P Device interface which will fail.

If a P2P_DEVICE is supported by the driver and update_config is used,
the P2P Device configuration data will override the main interface
configuration data.

Signed-hostap: Ilan Peer <ilan.peer@intel.com>