iwlwifi: pass NAPI struct from transport layer

The mac80211 patch to pass the NAPI struct only changed iwlwifi to
store the NAPI struct, but we can do better: pass it directly from
the lower transport layer to the opmode during RX, and then on to
mac80211 from there.

When we add multiple RX queues, we can then pass the appropriate
NAPI struct properly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>