mac80211: Fix signal strength average initialization for CQM events

mac80211: Fix signal strength average initialization for CQM events

The ave_beacon_signal value uses 1/16 dB unit and as such, must be
initialized with the signal level of the first Beacon frame multiplied
by 16. This fixes an issue where the initial CQM events are reported
incorrectly with a burst of events while the running average
approaches the correct value after the incorrect initialization. This
could cause user space -based roaming decision process to get quite
confused at the moment when we would like to go through authentication
and DHCP.

Cc: stable@kernel.org
Signed-off-by: Jouni Malinen <j@w1.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>