xen: return a per-mapping error from XENMEM_add_to_physmap_range.

xen: return a per-mapping error from XENMEM_add_to_physmap_range.

Since ARM and PVH dom0 kernel use this to map foreign domain pages
they could in the future hit paged out or shared pages etc and
therefore need to propagate which frames are -ENOENT and which failed
for some other reason.

We have not yet released a version of Xen with this particular
hypercall subop so we can change the interface without worrying about
compatibility (I think/hope).

This would be used by the privcmd driver, in particular it relates to
Mats' patch "improve performance of MMAPBATCH_V2."

NB I have only implemented the ARM side since the PVH side isn't in
tree yet.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: Mats Petersson <mats.petersson@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>