dm_op: convert HVMOP_track_dirty_vram

dm_op: convert HVMOP_track_dirty_vram

The handle type passed to the underlying shadow and hap functions is
changed for compatibility with the new hypercall buffer.

NOTE: This patch also modifies the type of the 'nr' parameter of
      xc_hvm_track_dirty_vram() from uint64_t to uint32_t. In practice
      the value passed was always truncated to 32 bits.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>