iwlmvm: set properly NIC_NOT_ACK_ENABLED flag

The STA_CTXT_HE_NIC_NOT_ACK_ENABLED flag tells the firmware
whether *we* support ack-enabled.
So what should be checked is our *own* capability and not
the *peer's* capability.

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
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.20210210171218.59f44e210096.I8f31968f6f7303255e212d869ca0131becd309aa@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>