xen/merge error: Re-introduce xen-platform-pci driver.

xen/merge error: Re-introduce xen-platform-pci driver.

The merge 98687483f3918349f96697261b491ee41b824871:

    Merge branch 'stable/not-upstreamed' into uek2-merge

    * stable/not-upstreamed:
      Xen: Export host physical CPU information to dom0
      xen/mce: Change the machine check point
      Add mcelog support from xen platform

    Conflicts:
    	drivers/xen/Kconfig
    	drivers/xen/Makefile

mismerged the Makefile. The end result that the line
obj-$(CONFIG_XEN_PVHVM) += platform_pci.o was removed
leading to no PVonHVM driver to tell QEMU to unplug the device.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>