vhost: Fix memory region section comparison

Using memcmp to compare structures wasn't safe,
as I found out on ARM when I was getting falce miscompares.

Use the helper function for comparing the MRSs.

Fixes: ade6d081 ("vhost: Regenerate region list from changed sections list")
Cc: qemu-stable@nongnu.org
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190814175535.2023-4-dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 3fc4a64c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>