nvmem: qfprom: Mark core clk as optional

On some platforms like sc7280 on non-ChromeOS devices the core clock
cannot be touched by Linux so we cannot provide it. Mark it as optional
as accessing qfprom for reading works without it but we still prohibit
writing if we cannot provide the clock.

Signed-off-by: Luca Weiss <[e-mail]>
Reviewed-by: Douglas Anderson <[e-mail]>
Signed-off-by: Srinivas Kandagatla <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/nvmem/qfprom.c

···
 		if (IS_ERR(priv->vcc))
 			return PTR_ERR(priv->vcc);
 
-		priv->secclk = devm_clk_get(dev, "core");
+		priv->secclk = devm_clk_get_optional(dev, "core");
 		if (IS_ERR(priv->secclk))
 			return dev_err_probe(dev, PTR_ERR(priv->secclk), "Error getting clock\n");
 
-		/* Only enable writing if we have SoC data. */
-		if (priv->soc_data)
+		/* Only enable writing if we have SoC data and a valid clock */
+		if (priv->soc_data && priv->secclk)
 			econfig.reg_write = qfprom_reg_write;
 	}