bootstd: Add a new bootmeth method to set the bootflow

Normally the bootmeth driver reads the bootflow from the bootdev, since
it knows the correct way to do it.

However it is easier for some bootdevs to handle this themselves. For
example, reading from SPI flash is quite different from other devices.

Add a way for the bootdev to pass a bootflow to the bootmeth, so that
this can be supported.

Signed-off-by: Simon Glass <sjg@chromium.org>

boot/bootmeth-uclass.c

@@ -50,6 +50,17 @@ int bootmeth_read_bootflow(struct udevice *dev, struct bootflow *bflow)
 	return ops->read_bootflow(dev, bflow);
 }
 
+int bootmeth_set_bootflow(struct udevice *dev, struct bootflow *bflow,
+			  char *buf, int size)
+{
+	const struct bootmeth_ops *ops = bootmeth_get_ops(dev);
+
+	if (!ops->set_bootflow)
+		return -ENOSYS;
+
+	return ops->set_bootflow(dev, bflow, buf, size);
+}
+
 int bootmeth_boot(struct udevice *dev, struct bootflow *bflow)
 {
 	const struct bootmeth_ops *ops = bootmeth_get_ops(dev);