iwlwifi: mvm: simplify __iwl_mvm_set_sta_key()

There's no need to differentiate identical default and cipher
type cases, nor do we really need to have a 'ret' variable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210802215208.e89178b22fbf.I4d62baad9a9fdfd5c645a3cc5dbffb22feab5033@changeid


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