vfio-user/container.h: update VFIOUserContainer declaration

Update the VFIOUserContainer declaration so that it is closer to our coding
guidelines: remove the explicit typedef (this is already handled by the
OBJECT_DECLARE_TYPE() macro) and add a blank line after the parent object.

Signed-off-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20250715093110.107317-9-mark.caveayland@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio-user/container.h

@@ -13,10 +13,11 @@
 #include "hw/vfio-user/proxy.h"
 
 /* MMU container sub-class for vfio-user. */
-typedef struct VFIOUserContainer {
+struct VFIOUserContainer {
     VFIOContainerBase bcontainer;
+
     VFIOUserProxy *proxy;
-} VFIOUserContainer;
+};
 
 OBJECT_DECLARE_SIMPLE_TYPE(VFIOUserContainer, VFIO_IOMMU_USER);