rtw89: 8852a: correct bit definition of dfs_en

Since there are other protections in the set channel flow, fortunately old
wrong setting won't affect the performance.

Signed-off-by: Chung-Hsuan Hung <hsuan8331@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211221024800.23814-1-pkshih@realtek.com