spi: bcm-qspi: Handle clock probe deferral

The clock provider may not be ready by the time spi-bcm-qspi gets
probed, handle probe deferral using devm_clk_get_optional().
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200420190853.45614-2-kdasu.kdev@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm-qspi.c

@@ -1227,6 +1227,11 @@ int bcm_qspi_probe(struct platform_device *pdev,
 	}
 
 	qspi = spi_master_get_devdata(master);
+
+	qspi->clk = devm_clk_get_optional(&pdev->dev, NULL);
+	if (IS_ERR(qspi->clk))
+		return PTR_ERR(qspi->clk);
+
 	qspi->pdev = pdev;
 	qspi->trans_pos.trans = NULL;
 	qspi->trans_pos.byte = 0;
@@ -1340,13 +1345,6 @@ int bcm_qspi_probe(struct platform_device *pdev,
 		qspi->soc_intc = NULL;
 	}
 
-	qspi->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(qspi->clk)) {
-		dev_warn(dev, "unable to get clock\n");
-		ret = PTR_ERR(qspi->clk);
-		goto qspi_probe_err;
-	}
-
 	ret = clk_prepare_enable(qspi->clk);
 	if (ret) {
 		dev_err(dev, "failed to prepare clock\n");