cfg80211: Add support to calculate and report 4096-QAM HE rates

cfg80211: Add support to calculate and report 4096-QAM HE rates

Drivers supporting 4096-QAM rates as a vendor extension in HE mode need
to update the correct rate info to userspace while using 4096-QAM (MCS12
and MCS13) in HE mode. Add support to calculate bitrates of HE-MCS12 and
HE-MCS13 which represent the 4096-QAM modulation schemes. The MCS12 and
MCS13 bitrates are defined in IEEE P802.11be/D0.1.

In addition, scale up the bitrates by 3*2048 in order to accommodate
calculations for the new MCS12 and MCS13 rates without losing fraction
values.

Signed-off-by: Vamsi Krishna <vamsin@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20201029183457.7005-1-jouni@codeaurora.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>