xen: remove the legacy 'xen_disk' backend

This backend has now been replaced by the 'xen-qdisk' XenDevice.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Acked-by: NAnthony Perard <anthony.perard@citrix.com>
Signed-off-by: NAnthony PERARD <anthony.perard@citrix.com>

hw/block/Makefile.objs

@@ -5,7 +5,6 @@ common-obj-$(CONFIG_NAND) += nand.o
 common-obj-$(CONFIG_PFLASH_CFI01) += pflash_cfi01.o
 common-obj-$(CONFIG_PFLASH_CFI02) += pflash_cfi02.o
 common-obj-$(CONFIG_XEN) += xen-block.o
-common-obj-$(CONFIG_XEN) += xen_disk.o
 common-obj-$(CONFIG_ECC) += ecc.o
 common-obj-$(CONFIG_ONENAND) += onenand.o
 common-obj-$(CONFIG_NVME_PCI) += nvme.o