cfg80211: Adjust 6 GHz frequency to channel conversion

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

Change-Id: I3a10fbef7ece7b86f44ac9bd09556f9d89d1844c
CRs-Fixed: 3183686
Signed-off-by: Amar Singhal <asinghal@codeaurora.org>
Link: https://lore.kernel.org/r/1592599921-10607-1-git-send-email-asinghal@codeaurora.org
Git-commit: 2d9b55508556ccee6410310fb9ea2482fd3328eb
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Madhvapathi Sriram <msriram@codeaurora.org>