iwlwifi: mvm: add support for GCMP encryption

Newer hardware supports GCMP and GCMP 256-bit ciphers.
Add support for adding/setting GCMP key for TX mode.

In the TX command handling GCMP-256 is handled in a different
way as the key size should be up to 128-bits:
Set the key value to the key index in the key table,
and specify that this key should be taken form the key table
instead of from the TX command.

While at it - convert security control flags to an enum.

Signed-off-by: Ayala Beker <ayala.beker@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>