iw: Add OCB mode handling

iw: Add OCB mode handling

Since the commit 6e0bd6c35b021dc73a81ebd1ef79761233c48b50
("cfg80211: 802.11p OCB mode handling") and
239281f803e2efdb77d906ef296086b6917e5d71
("mac80211: 802.11p OCB mode support")
does the Linux kernel support OCB mode. This commit adds
proper OCB mode handling.

Modify the command for device type setting to support OCB mode.
Add commands for "joining" and "leaving" the OCB mode network.
When joining two arguments are mandatory -- frequency and
channel bandwidth (5 or 10 MHz).

Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>