spi: fsi: add a missing of_node_put

'for_each_available_child_of_node' performs an of_node_get on each
iteration, so a return from the middle of the loop requires an of_node_put.

Fixes: bbb6b2f9 ("spi: Add FSI-attached SPI controller driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/504e431b900341249d331b868d90312cf41f415a.1618947919.git.christophe.jaillet@wanadoo.frSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsi.c

@@ -566,8 +566,10 @@ static int fsi_spi_probe(struct device *dev)
 			continue;
 
 		ctlr = spi_alloc_master(dev, sizeof(*ctx));
-		if (!ctlr)
+		if (!ctlr) {
+			of_node_put(np);
 			break;
+		}
 
 		ctlr->dev.of_node = np;
 		ctlr->num_chipselect = of_get_available_child_count(np) ?: 1;