iwlwifi: make some functions friendly to sparse

Somehow, sparse cannot track the cond_lock() here properly,
but if we return directly from the inner basic block then
it doesn't complain. Refactor the code a bit to make it not
complain.

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.20220130115024.3f9de2d59929.Ib6324e93951ee877754538c89f3ab2a84998bd40@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>