Use upstream qemu without distro's patches

  * Use distro's upstream qemu with xen configure instead patches.
  * Removed patches no more needed:
    - debian/patches/ubuntu-qemu-disable-qemu-upstream.diff
    - debian/patches/ubuntu-qemu-upstream-location.patch
  * Refreshed patches:
    - debian/patches/ubuntu-tools-armhf-without-ocaml.patch