iwlwifi: update support for 3168 series firmware and NVM

Update the struct which defines the support for 3168 cards.
Now it will search for a firmware of this format:
iwlwifi-3168-XX.ucode
Also, set the minimum version of the ucode to 20.
Update the minimum NVM version and minimum NVM calibrations
version of the 3168 series.

Signed-off-by: Oren Givon <oren.givon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>