clk: make ICST driver handle the VCO registers

It turns out that all platforms using the ICST VCO are really
just touching two registers, and in the same way as well: one
register with the VCO configuration as such, and one lock register
that makes it possible to write to the VCO.

Factor this register read/write into the ICST driver so we can
reuse it in the IM-PD1 driver.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/versatile/clk-icst.h

@@ -1,10 +1,18 @@
 #include <asm/hardware/icst.h>
 
+/**
+ * struct clk_icst_desc - descriptor for the ICST VCO
+ * @params: ICST parameters
+ * @vco_offset: offset to the ICST VCO from the provided memory base
+ * @lock_offset: offset to the ICST VCO locking register from the provided
+ *	memory base
+ */
 struct clk_icst_desc {
 	const struct icst_params *params;
-	struct icst_vco (*getvco)(void);
-	void (*setvco)(struct icst_vco);
+	u32 vco_offset;
+	u32 lock_offset;
 };
 
 struct clk *icst_clk_register(struct device *dev,
-			      const struct clk_icst_desc *desc);
+			      const struct clk_icst_desc *desc,
+			      void __iomem *base);