wireless: only use alpha2 regulatory information from country IE

The meaning and/or usage of the country IE is somewhat poorly defined.
In practice, this means that regulatory rulesets in a country IE are
often incomplete and might be untrustworthy.  This removes the code
associated with interpreting those rulesets while preserving respect
for country "alpha2" codes also contained in the country IE.

Signed-off-by: John W. Linville <linville@tuxdriver.com>