davinci: da850: add a .set_rate method to ref_clk

This patch allows setting the input clock frequency of the SoC from
the board specific code using the davinci_set_refclk_rate function.
Suggested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Christian Riesch <christian.riesch@omicron.at>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

arch/arm/mach-davinci/da850.c

@@ -58,6 +58,7 @@ static struct pll_data pll0_data = {
 static struct clk ref_clk = {
 	.name		= "ref_clk",
 	.rate		= DA850_REF_FREQ,
+	.set_rate	= davinci_simple_set_rate,
 };
 
 static struct clk pll0_clk = {