iwlwifi: fix __percpu annotation

Sparse warns about some type mismatches, which really is just
because of the strangely placed __percpu annotation. Put it
into the correct place.

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.20210819183728.0a292b05fcf4.I7e89dfa6495143585021cb628ebb17d52e4588e5@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>