Fix the error that mcs will be reduced to a range of 0 to 7 in ht mode.
Fixes: 70fd1333cd32 ("mt76: mt7915: rework .set_bitrate_mask() to support more options")
Signed-off-by: Howard Hsu <[email protected]>
Signed-off-by: Felix Fietkau <[email protected]>
