iwlwifi: update MAINTAINERS entry

Reflect the fact that the linuxwifi@intel.com address will disappear,
and that neither Emmanuel nor myself are really much involved with
the maintenance these days.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20201129151117.a25afe6d2c7f.I8f13a5689dd353825fb2b9bd5b6f0fbce92cb12b@changeid