iwlwifi: mvm: deprecate -7 firmware

This firmware is not supported any more.
A few code paths specific to old firmware can be removed.
We can now assume that a few TLV flags are always set since
we won't load firmware that didn't support the corresponding
features. This will be done in a separate patch.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>