iwlwifi: parse command version TLV

In newer firmware images there's a command version TLV that
states, for each listed command or notification, which version
of the command and/or notification structure is used. Read and
keep this data to be able to use it in the future.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>