conf: fixup USB input bus check
conf: fixup USB input bus check

This patch fixes the USB input bus check, the bug was introduced by commit 317badb

Signed-off-by: Xiao Feng Ren <26b198131b8034227804075638124b63cd4351e6@linux.vnet.ibm.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Signed-off-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

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