Unless NL80211_BAND_ATTR_HT_CAPA is defined, assume we don't have

Unless NL80211_BAND_ATTR_HT_CAPA is defined, assume we don't have
channel-type-setting capabilities, and don't build the code to set the
channel type or fetch any channel types other than "no HT".

(It *looks* as if nl80211.h defines NL80211_BAND_ATTR_HT_CAPA as a
member of an enum *and* as a #define, at least in the kernels I've
looked at, so we can test for it with #ifdef - perhaps that's *why* it's
#defined.)

svn path=/trunk/; revision=43608