Allow empty passwords login so that the default root user can login in
through openssh.
(From OE-Core rev: 39ef0a705ca059f9a7c68aa1710c81411fb7c762)
Signed-off-by: Lianhao Lu <lianhao.lu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>