iwlwifi: stop_hw replace enable_rfkill_int

This trans_ops->stop_hw leaves the RFKILL interrupt enabled,
we can call that one instead of enable_rfkill_int. By that,
we reduce the numbers of acceesses to the NIC from the upper
layers.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>