Add support for Qemu rocker switch

[troglobit]

Latest versions of Qemu now have fixed previous issues with rocker.

New syntax: -device '{"driver":"rocker","ports":["dev0","dev1"]}'

See https://gitlab.com/qemu-project/qemu/-/commit/b06f8b500da2a5a73dfb15de17cd96ad2385fdc7