iwlwifi: mvm: fix wrong DCM TLC config

When configuring TLC DCM flag:
1. check the peer's RX DCM capabilities (since we TX)
2. do not set DCM_NSS_2 since we do not support it

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Fixes: 423584dd ("iwlwifi: rs-fw: support dcm")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>