spi: stm32-qspi: defer probe for reset controller

Changes stm32 QSPI driver to defer its probe operation when a reset
controller device have not yet probed but is registered in the
system.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Link: https://lore.kernel.org/r/20200203135048.1299-2-patrice.chotard@st.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32-qspi.c

@@ -615,7 +615,11 @@ static int stm32_qspi_probe(struct platform_device *pdev)
 	}
 
 	rstc = devm_reset_control_get_exclusive(dev, NULL);
-	if (!IS_ERR(rstc)) {
+	if (IS_ERR(rstc)) {
+		ret = PTR_ERR(rstc);
+		if (ret == -EPROBE_DEFER)
+			goto err;
+	} else {
 		reset_control_assert(rstc);
 		udelay(2);
 		reset_control_deassert(rstc);