Use openbmc/qemu for qemu recipe

[mx-shift]

When building an image or attempting to use runqemu, the upstream qemu is built by bitbake. Since all of the Aspeed and machine-specific (palmetto, witherspoon) support is in openbmc/qemu, that repo should be used by the qemu recipe instead.

[amboar]

I had some patches for this a long time back. Probably worth starting afresh though.

[stale]

This issue has been automatically marked as stale because no activity has occurred in the last 6 months. It will be closed if no activity occurs in the next 30 days. If this issue should not be closed please add a comment. Thank you for your understanding and contributions.

[amboar]

Closing this as we have decent support upstream, and we should be working to upstream our patches.