wifi: iwlwifi: cfg: disable STBC for BL step A devices

The A step of BL devices doesn't support STBC, so we need to disable
it.

Create new HT params and a macro to use specifically with BL A-step
devices where STBC is disabled.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20221102165239.806dbfa53f40.I4b14a8be30795bdcd73686bd1f9222e7ab93b505@changeid