ath11k: add 6G frequency list supported by driver

This patch adds support for 6GHz frequency listing.

Signed-off-by: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200603001724.12161-2-pradeepc@codeaurora.org