arm/xen: Export phys_to_mach to fix Xen module link errors
arm/xen: Export phys_to_mach to fix Xen module link errors

Various xen drivers fail to link when built as modules with the following
error:

ERROR: "phys_to_mach" [drivers/xen/xen-gntalloc.ko] undefined!
ERROR: "phys_to_mach" [drivers/net/xen-netfront.ko] undefined!
ERROR: "phys_to_mach" [drivers/net/xen-netback/xen-netback.ko] undefined!
ERROR: "phys_to_mach" [drivers/block/xen-blkfront.ko] undefined!

The mfn_to_pfn and pfn_to_mfn functions get inlined in these modules and
those functions require phys_to_mach.  Export the symbol to fix the link
errors.

Signed-off-by: Josh Boyer <94755a79aca753e683bb6d0e796d473b797056eb@fedoraproject.org>
Signed-off-by: Stefano Stabellini <22a0c6385d750d07aa383c9f813cf6f0228657d8@eu.citrix.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs