authsae: Use kbit/s as mcast_rate unit like wpad

authsae: Use kbit/s as mcast_rate unit like wpad

The OpenWrt wireless configuration for mcast_rate is defined as Kbit/s when
using wpa_supplicant for IBSS/802.11s and iw for unencrypted IBSS/802.11s.
But when using authsae, the unit for the same option is redefined as
Mbit/s. Better use the same unit for this option independent of the backend
which is used.

Old values for mcast_rate (< 1000) are still interpreted Mbit/s to avoid
problems during upgrades from older versions.

Signed-off-by: Sven Eckelmann <sven@open-mesh.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47614 3c298f89-4303-0410-b956-a3cf2f4a3e73