qemu: Fixed running QEMU with virtio error reporting

qemu: Fixed running QEMU with virtio error reporting

If vhost_net module is not properly installed,
runqemu script will report the error and
provide the user with a link to the guide.
Also corrected small cosmetic issues in
runqemu script messages.
Also removed <> (read/write) check.

Fixes [YOCTO #3184]

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