rtw88: rtw8821c: enable rfe 6 devices

Ping-Ke Shih answered[1] a question for a user about an rtl8821ce device that
reported RFE 6, which the driver did not support. Ping-Ke suggested a possible
fix, but the user never reported back.

A second user discovered the above thread and tested the proposed fix.
Accordingly, I am pushing this change, even though I am not the author.

[1] https://lore.kernel.org/linux-wireless/3f5e2f6eac344316b5dd518ebfea2f95@realtek.com/



Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Reported-and-tested-by: masterzorag <masterzorag@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220107024739.20967-1-Larry.Finger@lwfinger.net