rtlwifi: rtl8192cu: Fix spelling mistake "writting" -> "writing"

There are some spelling mistakes in the comments. Fix it.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220411032458.2517551-1-lv.ruyi@zte.com.cn