cfg80211: initialize on-stack chandefs

In a few places we don't properly initialize on-stack chandefs,
resulting in EDMG data to be non-zero, which broke things.

Additionally, in a few places we rely on the driver to init the
data completely, but perhaps we shouldn't as non-EDMG drivers
may not initialize the EDMG data, also initialize it there.

Cc: stable@vger.kernel.org
Fixes: 2a38075c ("nl80211: Add support for EDMG channels")
Reported-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/1569239475-I2dcce394ecf873376c386a78f31c2ec8b538fa25@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>