wifi: iwlwifi: mvm: make internal callback structs const

There's no need for these to be writable, so they can
be const (and static).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230524203151.c41eb6687868.I2dac1158e5723187bda1973aa49fde8a794621c8@changeid


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