qemux86: Support for KVM, paravirt and virtio added

qemux86: Support for KVM, paravirt and virtio added

KVM, paravirtualization and virtio drivers are now activated
in runqemu using the kvm option flag for qemux86.
Host CPU features are also exported to guest OS (Yocto Linux).
Usage example: runqemu qemux86 core-image-x11 kvm

Implements [YOCTO #2550].

(From OE-Core rev: a35d03e2eb905de4eadc9c7df5b50bff1fb7f897)

Signed-off-by: Cristian Iorga <cristian.iorga@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>