wireless: add peer-to-peer related definitions

The Peer-to-Peer IE is vendor-specific IE identified by WiFi Alliance
OUI and specific P2P OUI type. The payload of this IE consists of
so-called P2P attributes. This patch adds definitions for processing
these attributes.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>