dm: core: Update uclass_find_next_free_req_seq() args

At present this is passed a uclass ID and it has to do a lookup. The
callers all have the uclass pointer, except for the I2C uclass where the
code will soon be deleted.

Update the argument to a uclass * instead of an ID since it is more
efficient.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/i2c/designware_i2c_pci.c b/drivers/i2c/designware_i2c_pci.c
index 8d7b1fe..3c15320 100644
--- a/drivers/i2c/designware_i2c_pci.c
+++ b/drivers/i2c/designware_i2c_pci.c
@@ -90,7 +90,9 @@
 
 static int designware_i2c_pci_bind(struct udevice *dev)
 {
+	struct uclass *uc;
 	char name[20];
+	int ret;
 
 	if (dev_of_valid(dev))
 		return 0;
@@ -108,7 +110,11 @@
 	 * be possible. We cannot use static data in drivers since they may be
 	 * used in SPL or before relocation.
 	 */
-	dev->req_seq = uclass_find_next_free_req_seq(UCLASS_I2C);
+	ret = uclass_get(UCLASS_I2C, &uc);
+	if (ret)
+		return ret;
+
+	dev->req_seq = uclass_find_next_free_req_seq(uc);
 	sprintf(name, "i2c_designware#%u", dev->req_seq);
 	device_set_name(dev, name);