iwlwifi: pcie: introduce new stop_device

This function is basically the same as gen1, except for clean
ups of old devices configuration that are never used in a000
configuration.
It will also help with refactoring rf_kill later on.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>