wifi: iwlwifi: mvm: put only a single IGTK into FW

The firmware only supports a single IGTK, and due to some
changes it really doesn't like to have multiple programmed
in later versions. Since only newer firmware cannot remove
a key that isn't present any more, adjust only the MLD API
code to keep track of the previous IGTK and remove it when
a new one is added.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230613155501.3fde1ef09270.I2e12a3b0bba4325c07dc8fcce39b711f158bd621@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>