don't use 'Yoda conditions'

imitate nearby code about using '!value' or 'value == NULL'
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

qdev-monitor.c

@@ -694,7 +694,7 @@ void qmp_device_del(const char *id, Error **errp)
     DeviceState *dev;
 
     dev = qdev_find_recursive(sysbus_get_default(), id);
-    if (NULL == dev) {
+    if (!dev) {
         error_set(errp, QERR_DEVICE_NOT_FOUND, id);
         return;
     }

qemu-char.c

@@ -4121,7 +4121,7 @@ void qmp_chardev_remove(const char *id, Error **errp)
     CharDriverState *chr;
 
     chr = qemu_chr_find(id);
-    if (NULL == chr) {
+    if (chr == NULL) {
         error_setg(errp, "Chardev '%s' not found", id);
         return;
     }

util/qemu-sockets.c

@@ -732,7 +732,7 @@ int unix_connect_opts(QemuOpts *opts, Error **errp,
     ConnectState *connect_state = NULL;
     int sock, rc;
 
-    if (NULL == path) {
+    if (path == NULL) {
         error_setg(errp, "unix connect: no path specified");
         return -1;
     }