Minor README fix for supported drivers
Minor README fix for supported drivers

Change-Id: Ib8ad249a14ee694c169e334d4d20c0aef1046c6a

EntropyWorks/bifrost,devananda/bifrost,EntropyWorks/bifrost,devananda/bifrost,openstack/bifrost,bcornec/bifrost,openstack/bifrost,bcornec/bifrost