wifi: rtw88: Extend TX power stuff for 3-4 spatial streams

Although the RTL8814AU only has 3 spatial streams, maybe some other chip
has 4.

Correct the TX power index and TX power limit calculations for 3SS and
4SS HT/VHT rates.

With this the RTL8814AU can set the TX power correctly.

Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/d0c0e126-0794-4c4e-9203-ea39a707b673@gmail.com