BACKPORT: cfg80211: Adjust 6 GHz frequency to channel conversion

Adjust the 6 GHz frequency to channel conversion function,
the other way around was previously handled.

Signed-off-by: Amar Singhal <asinghal@codeaurora.org>
Link: https://lore.kernel.org/r/1592599921-10607-1-git-send-email-asinghal@codeaurora.org


[rewrite commit message, hard-code channel 2]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Bug: 167126230
(cherry picked from commit 2d9b55508556ccee6410310fb9ea2482fd3328eb)
Change-Id: Ieb788ea5a5ad614651c1a2c83d2c0fc16a98e00f
Signed-off-by: Vamsi Krishna <vamsin@codeaurora.org>