xen: Introduce VGA sync dirty bitmap support

This patch introduces phys memory client for Xen.

Only sync dirty_bitmap and set_memory are actually implemented.
migration_log will stay empty for the moment.

Xen can only log one range for bit change, so only the range in the
first call will be synced.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

trace-events

diff --git a/trace-events b/trace-events
index f1230f1..46a19d3 100644
--- a/trace-events
+++ b/trace-events
@@ -396,6 +396,7 @@
 
 # xen-all.c
 disable xen_ram_alloc(unsigned long ram_addr, unsigned long size) "requested: %#lx, size %#lx"
+disable xen_client_set_memory(uint64_t start_addr, unsigned long size, unsigned long phys_offset, bool log_dirty) "%#"PRIx64" size %#lx, offset %#lx, log_dirty %i"
 
 # xen-mapcache.c
 disable qemu_map_cache(uint64_t phys_addr) "want %#"PRIx64""