Add override ability to qemu to allow qemu specific
configurations for any qemu machine.
(From OE-Core rev: 4ee668a558e5d4a6d14e29c9fe88b8bb642a16a9)
Signed-off-by: Cristian Iorga <cristian.iorga@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>