arm64: Attach the vgic even if there is no ITS

If there is no ITS device so no memory resources the gicv3 driver would
exit attaching early. This caused the vgic driver to also not be
attached, even if it could.

Reported by:	novel@
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D54791

sys/arm64/arm64/gic_v3_fdt.c

@@ -86,7 +86,7 @@ EARLY_DRIVER_MODULE(gic_v3, ofwbus, gic_v3_fdt_driver, 0, 0,
 /*
  * Helper functions declarations.
  */
-static int gic_v3_ofw_bus_attach(device_t);
+static void gic_v3_ofw_bus_attach(device_t);
 
 /*
  * Device interface.
@@ -193,12 +193,7 @@ gic_v3_fdt_attach(device_t dev)
 	 * GIC will act as a bus in that case.
 	 * Failure here will not affect main GIC functionality.
 	 */
-	if (gic_v3_ofw_bus_attach(dev) != 0) {
-		if (bootverbose) {
-			device_printf(dev,
-			    "Failed to attach ITS to this GIC\n");
-		}
-	}
+	gic_v3_ofw_bus_attach(dev);
 
 	if (device_get_children(dev, &sc->gic_children, &sc->gic_nchildren) != 0)
 		sc->gic_nchildren = 0;
@@ -298,7 +293,7 @@ gic_v3_ofw_fill_ranges(phandle_t parent, struct gic_v3_softc *sc,
  * Collects and configures device informations and finally
  * adds ITS device as a child of GICv3 in Newbus hierarchy.
  */
-static int
+static void
 gic_v3_ofw_bus_attach(device_t dev)
 {
 	struct gic_v3_ofw_devinfo *di;
@@ -313,8 +308,13 @@ gic_v3_ofw_bus_attach(device_t dev)
 	if (parent > 0) {
 		rv = gic_v3_ofw_fill_ranges(parent, sc, &addr_cells,
 		    &size_cells);
-		if (rv != 0)
-			return (rv);
+		if (rv != 0) {
+			if (bootverbose) {
+				device_printf(dev,
+				    "Failed to attach ITS to this GIC\n");
+			}
+			goto vgic;
+		}
 
 		/* Iterate through all GIC subordinates */
 		for (node = OF_child(parent); node > 0; node = OF_peer(node)) {
@@ -369,28 +369,31 @@ gic_v3_ofw_bus_attach(device_t dev)
 			sc->gic_nchildren++;
 			device_set_ivars(child, di);
 		}
-	}
 
-	/*
-	 * If there is a vgic maintanance interrupt add a virtual gic
-	 * child so we can use this in the vmm module for bhyve.
-	 */
-	if (OF_hasprop(parent, "interrupts")) {
-		child = device_add_child(dev, "vgic", DEVICE_UNIT_ANY);
-		if (child == NULL) {
-			device_printf(dev, "Could not add vgic child\n");
-		} else {
-			di = malloc(sizeof(*di), M_GIC_V3, M_WAITOK | M_ZERO);
-			resource_list_init(&di->di_rl);
-			di->di_gic_dinfo.gic_domain = -1;
-			di->di_gic_dinfo.is_vgic = 1;
-			device_set_ivars(child, di);
-			sc->gic_nchildren++;
+vgic:
+
+		/*
+		 * If there is a vgic maintanance interrupt add a virtual gic
+		 * child so we can use this in the vmm module for bhyve.
+		 */
+		if (OF_hasprop(parent, "interrupts")) {
+			child = device_add_child(dev, "vgic", DEVICE_UNIT_ANY);
+			if (child == NULL) {
+				device_printf(dev,
+				    "Could not add vgic child\n");
+			} else {
+				di = malloc(sizeof(*di), M_GIC_V3,
+				    M_WAITOK | M_ZERO);
+				resource_list_init(&di->di_rl);
+				di->di_gic_dinfo.gic_domain = -1;
+				di->di_gic_dinfo.is_vgic = 1;
+				device_set_ivars(child, di);
+				sc->gic_nchildren++;
+			}
 		}
 	}
 
 	bus_attach_children(dev);
-	return (0);
 }
 
 static struct resource_list *