stand/kshim: Implement bus_detach_children

While here, update bus_generic_detach to delete devices as in the
kernel.

Reviewed by:	imp, markj
Differential Revision:	https://reviews.freebsd.org/D48410

stand/kshim/bsd_kernel.c

@@ -664,7 +664,7 @@ device_get_unit(device_t dev)
 }
 
 int
-bus_generic_detach(device_t dev)
+bus_detach_children(device_t dev)
 {
 	device_t child;
 	int error;
@@ -679,6 +679,17 @@ bus_generic_detach(device_t dev)
 	return (0);
 }
 
+int
+bus_generic_detach(device_t dev)
+{
+	int error;
+
+	error = bus_detach_children(dev);
+	if (error == 0)
+		error = device_delete_children(dev);
+	return (error);
+}
+
 const char *
 device_get_nameunit(device_t dev)
 {

stand/kshim/bsd_kernel.h

@@ -650,6 +650,7 @@ void bus_release_resources(device_t, const struct resource_spec *,
     struct resource **);
 struct resource *bus_alloc_resource_any(device_t, int, int *, unsigned int);
 void bus_attach_children(device_t);
+int bus_detach_children(device_t);
 bus_space_tag_t rman_get_bustag(struct resource *);
 bus_space_handle_t rman_get_bushandle(struct resource *);
 u_long rman_get_size(struct resource *);