iw: util: factor out HE capability parser
iw: util: factor out HE capability parser

We're going to use this for scan parsing.

Signed-off-by: Brian Norris <67059238af8e1945c40edb274ce1d51ba595dbf3@chromium.org>
Link: https://lore.kernel.org/r/20201118033936.3667788-3-67059238af8e1945c40edb274ce1d51ba595dbf3@chromium.org
Signed-off-by: Johannes Berg <bff32994ff0f8d048f262a8388145a71b6071bfe@intel.com>

greearb/iw-ct,greearb/iw-ct