Bluedroid: Avoid multicast address for tun-tap interface

Linux Kernel disallows to set an ethernet multicast
address as ethernet device address.

The IEEE has specified that the most significant bit
of the most significant byte of a mac address is used
for multicast. If its a 1, that means multicast, 0
means unicast.

Bluedroid uses the BD address to set the tun-tap intf
mac address. This BD address can be randomly auto
generated, possibly with the multicast bit.

To avoid any address issue, this patch masks this bit
before setting the ethernet mac address.

Change-Id: Ifff4ec7237ae6cbef3b8d4c23096c5df65e1431c
Signed-off-by: Loic Poulain <loic.poulain@intel.com>
Reviewed-on: https://android.intel.com/184768


Reviewed-by: Zhang, Jianxun <jianxun.zhang@intel.com>
Tested-by: Zhang, Jianxun <jianxun.zhang@intel.com>