[ Upstream commit 80df9be67c44cb636bbc92caeddad8caf334c53c ]

Fixes a harmless underflow issue when CCK rates are actively being used
Signed-off-by: NFelix Fietkau <nbd@nbd.name>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>