nl80211: Use different attrs for BSSID and random MAC addr in scan req

NL80211_ATTR_MAC was used to set both the specific BSSID to be scanned
and the random MAC address to be used when privacy is enabled. When both
the features are enabled, both the BSSID and the local MAC address were
getting same value causing Probe Request frames to go with unintended
DA. Hence, this has been fixed by using a different NL80211_ATTR_BSSID
attribute to set the specific BSSID (which was the more recent addition
in cfg80211) for a scan.

Backwards compatibility with old userspace software is maintained to
some extent by allowing NL80211_ATTR_MAC to be used to set the specific
BSSID when scanning without enabling random MAC address use.

Scanning with random source MAC address was introduced by commit
ad2b26ab ("cfg80211: allow drivers to support random MAC addresses
for scan") and the issue was introduced with the addition of the second
user for the same attribute in commit 818965d3 ("cfg80211: Allow a
scan request for a specific BSSID").

Fixes: 818965d3 ("cfg80211: Allow a scan request for a specific BSSID")
Signed-off-by: Vamsi Krishna <vamsin@qti.qualcomm.com>
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>