netd: add support for legacy hostapd

Implements BOARD_HAVE_LEGACY_HOSTAPD, to avoid passing
"ieee80211n=1" to hostapd config.

Change-Id: I93769bb4059197c4b2c68782dafa314166970cc9
netd: workaround to skip wifi fw reload

Implements BOARD_WLAN_NO_FWRELOAD, needed for some drivers that
do not support firmware reload (such as ar6000/ath6kl).

(cherry picked from commit 042870889a60b195227e5bc887d67f1490087715)

Change-Id: Icd175d45e3bc3297660b5cb9aa9c7af02d9e7a68