iwlwifi: mvm: set properly station flags in STA_HE_CTXT_CMD

For ACK_ENABLED and 32BIT_BA_BITMAP flags check the station capabilities
rather than bss_conf.ack_enabled and bss_conf.multi_sta_back_32bit.
These fields are stations capabilities and should not be in bss_conf.
Also note that the bss_conf flags are set in station mode only.
In the next patch I will remove ack_enabled and multi_sta_back_32bit
from the bss_conf structure.

Signed-off-by: Shaul Triebitz <shaul.triebitz@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200424182644.bc7230b74f93.I144f73cd6a797a7060429981fee62572861bc76b@changeid