vl.c: convert *vga_enabled functions to QOM

And get rid of qdev_exists().
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

hw/qdev.c

@@ -52,11 +52,6 @@ const char *qdev_fw_name(DeviceState *dev)
     return object_get_typename(OBJECT(dev));
 }
 
-bool qdev_exists(const char *name)
-{
-    return !!object_class_by_name(name);
-}
-
 static void qdev_property_add_legacy(DeviceState *dev, Property *prop,
                                      Error **errp);
 

hw/qdev.h

@@ -153,7 +153,6 @@ typedef struct GlobalProperty {
 
 DeviceState *qdev_create(BusState *bus, const char *name);
 DeviceState *qdev_try_create(BusState *bus, const char *name);
-bool qdev_exists(const char *name);
 int qdev_device_help(QemuOpts *opts);
 DeviceState *qdev_device_add(QemuOpts *opts);
 int qdev_init(DeviceState *dev) QEMU_WARN_UNUSED_RESULT;

vl.c

@@ -1700,17 +1700,18 @@ static const QEMUOption qemu_options[] = {
 
 static bool vga_available(void)
 {
-    return qdev_exists("VGA") || qdev_exists("isa-vga");
+    return object_class_by_name("VGA") || object_class_by_name("isa-vga");
 }
 
 static bool cirrus_vga_available(void)
 {
-    return qdev_exists("cirrus-vga") || qdev_exists("isa-cirrus-vga");
+    return object_class_by_name("cirrus-vga")
+           || object_class_by_name("isa-cirrus-vga");
 }
 
 static bool vmware_vga_available(void)
 {
-    return qdev_exists("vmware-svga");
+    return object_class_by_name("vmware-svga");
 }
 
 static void select_vgahw (const char *p)