hmp: Remove migration capabilities from "info migrate"

With the growth of migration capabilities, it is not proper to display
them in "info migrate". Users are recommended to use "info
migrate_capabiltiies" to list them.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Suggested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Message-Id: <20190806003645.8426-1-richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>