allow regdb keys shipped with the kernel

configname: CONFIG_CFG80211_USE_KERNEL_REGDB_KEYS

Linux Kernel Configuration
└─>Networking support
└─>Wireless
└─>allow regdb keys shipped with the kernel
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Allow the regulatory database to be signed by one of the keys for
which certificates are part of the kernel sources
(in net/wireless/certs/).

This is currently only Seth Forshee's key, who is the regulatory
database maintainer.