wifi: rtw88: 8822c: Fix reported RX band width

wifi: rtw88: 8822c: Fix reported RX band width

"iw dev wlp2s0 station dump" shows incorrect rx bitrate:

tx bitrate:     866.7 MBit/s VHT-MCS 9 80MHz short GI VHT-NSS 2
rx bitrate:     86.7 MBit/s VHT-MCS 9 VHT-NSS 1

This is because the RX band width is calculated incorrectly. Fix the
calculation according to the phydm_rxsc_2_bw() function from the
official drivers.

After:

tx bitrate:     866.7 MBit/s VHT-MCS 9 80MHz short GI VHT-NSS 2
rx bitrate:     390.0 MBit/s VHT-MCS 9 80MHz VHT-NSS 1

It also works correctly with the AP configured for 20 MHz and 40 MHz.

Tested with RTL8822CE.

Cc: stable@vger.kernel.org
Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/bca8949b-e2bd-4515-98fd-70d3049a0097@gmail.com