iwlwifi: remove max_vht_ampdu_exponent config parameter

This is not (or no longer) used, so remove it.

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.20210210171218.ed18d7c8e7b8.Ic3fdf7c8636f332e3d5ee5841b03bf85e3bc4855@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>