map_wiphy made the assumption that phy names follow the "phyN" pattern
but phys created or renamed by the "iw" command can have arbitrary
names. It seems that /sys/class/rfkill/rfkill%u/name is not updated on
a phy rename, so we can't use it to subsequently read
/sys/class/ieee80211/<name>/index but both
/sys/class/rfkill/rfkill%u/../index and
/sys/class/rfkill/rfkill%u/device/index point to that file.
Add rfkill.c/rfkill.h to be used for watching per-wiphy RFkill state.
It uses both /dev/rfkill and /sys because /dev/rfkill is the recommended
way of interfacing with rfkill but at the same time it doesn't provide
the information on mapping to wiphy IDs.
