wireless: remove struct regdom hinting

The code needs to be split out and cleaned up, so as a
first step remove the capability, to add it back in a
subsequent patch as a separate function. Also remove the
publically facing return value of the function and the
wiphy argument. A number of internal functions go from
being generic helpers to just being used for alpha2
setting.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>