clk: fix compile for OF && !COMMON_CLK

With commit 766e6a4ec6 (clk: add DT clock binding support),
compiling with OF && !COMMON_CLK is broken.

Reported-by: Alexandre Pereira da Silva <aletes.xgr@gmail.com>
Reported-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clkdev.c

@@ -24,7 +24,7 @@
 static LIST_HEAD(clocks);
 static DEFINE_MUTEX(clocks_mutex);
 
-#ifdef CONFIG_OF
+#if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
 struct clk *of_clk_get(struct device_node *np, int index)
 {
 	struct of_phandle_args clkspec;