iwlwifi: remove references to unsupported HW

There are still some references to 3945 and 4965 HW, which were never
supported in iwlwifi.  These references were inherited from a previous
project and are irrelevant here.  Additionally, remove some irrelevant
references to 5100 HW.  Remove all these.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>