clk: Add missing of_clk_set_defaults export

The of_clk_set_defaults() function is used in subsystems which can
be built as module. Add the missing symbol export entry so there
is no build errors like:
"ERROR: "of_clk_set_defaults" [drivers/i2c/i2c-core.ko] undefined!".

Fixes commit: 86be408bfbd846fab3c4ac21d6f9298bd2e4b790
"clk: Support for clock parents and rates assigned from device tree"

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
index 4e1bda7..aad4796 100644
--- a/drivers/clk/clk-conf.c
+++ b/drivers/clk/clk-conf.c
@@ -141,3 +141,4 @@
 
 	return __set_clk_rates(node, clk_supplier);
 }
+EXPORT_SYMBOL_GPL(of_clk_set_defaults);