wifi: iwlwifi: mvm: only clients can be 20MHz-only

Since only clients to an AP can be 20MHz-only STAs, adjust the
code to not make the use of EHT capabilities depend on only the
bandwidth, but also the type of interface.

Fixes: 701404f1 ("wifi: iwlwifi: rs: add support for parsing max MCS per NSS/BW in 11be")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230417113648.a3a4c931e4a3.I693a07f4d88044c889eee04793883a83bc5ee362@changeid


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