cfg80211: add firmware and hardware version to wiphy

It's useful to provide firmware and hardware version to user space and have a
generic interface to retrieve them. Users can provide the version information
in bug reports etc.

Add fields for firmware and hardware version to struct wiphy.

(Dropped nl80211 bits for now and modified remaining bits in favor of
ethtool. -- JWL)

Cc: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>