staging:r8188eu: remove unused definitions from include/ieee80211.h

Remove unused RTW_IEEE80211_FCTL_*, RTW_IEEE80211_FTYPE_*,
RTW_IEEE80211_STYPE_*, IEEE80211_STATMASK_*, IEEE80211_DEFAULT_*,
BEACON_PROBE_SSID_ID_POSITION, MFIE_TYPE_*, IEEE80211_DTIM_*
and IEEE80211_PS_*.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>