ath11k: add channel 2 into 6 GHz channel list

Add support for the 6 GHz channel 2 with center frequency 5935 MHz and
operating class 136 per IEEE Std 802.11ax-2021, Table E-4.

Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210722102054.43419-1-jouni@codeaurora.org