qemu: command: Remove dead code when formatting -drive
qemu: command: Remove dead code when formatting -drive

busid and unitid are ever used only if the device is an SD card due to
the check in qemuDiskBusNeedsDeviceArg. Since the SD card does not have
an bus or unit number, most of the code and command line formatter can
be removed since it will never be used.

crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,eskultety/libvirt,jfehlig/libvirt,crobinso/libvirt,andreabolognani/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jfehlig/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,olafhering/libvirt,eskultety/libvirt,libvirt/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,zippy2/libvirt,crobinso/libvirt,jardasgit/libvirt,jardasgit/libvirt,jardasgit/libvirt,jardasgit/libvirt,nertpinx/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,zippy2/libvirt,eskultety/libvirt,zippy2/libvirt,olafhering/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,libvirt/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,eskultety/libvirt,eskultety/libvirt,crobinso/libvirt,zippy2/libvirt,nertpinx/libvirt