mac80211: TX legacy rate control for Beacon frames

Use the Beacon frame specific legacy rate configuration, if specified
for AP or mesh, instead of the generic rate mask when selecting the TX
rate for Beacon frames.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200425155713.25687-4-jouni@codeaurora.org


Signed-off-by: Johannes Berg <johannes.berg@intel.com>