clk: sunxi: Give sunxi_factors_register a registers parameter

Before this commit sunxi_factors_register uses of_iomap(node, 0) to get
the clk registers. The sun6i prcm has factor clocks, for which we want to
use sunxi_factors_register, but of_iomap(node, 0) does not work for the prcm
factor clocks, because the prcm uses the mfd framework, so the registers
are not part of the dt-node, instead they are added to the platform_device,
as platform_device resources.

This commit makes getting the registers the callers duty, so that
sunxi_factors_register can be used with mfd instantiated platform device too.

While at it also add error checking to the of_iomap calls.

This commit also drops the __init function from sunxi_factors_register since
platform driver probe functions are not __init.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/clk/sunxi/clk-sunxi.c

@@ -728,7 +728,16 @@ static const struct factors_data sun7i_a20_out_data __initconst = {
 static struct clk * __init sunxi_factors_clk_setup(struct device_node *node,
 						   const struct factors_data *data)
 {
-	return sunxi_factors_register(node, data, &clk_lock);
+	void __iomem *reg;
+
+	reg = of_iomap(node, 0);
+	if (!reg) {
+		pr_err("Could not get registers for factors-clk: %s\n",
+		       node->name);
+		return NULL;
+	}
+
+	return sunxi_factors_register(node, data, &clk_lock, reg);
 }