clk: samsung: Fix compilation error

Fixes the below compilation error during non-dt build.
drivers/clk/samsung/clk.c: In function 'samsung_clk_of_register_fixed_ext':
drivers/clk/samsung/clk.c:252:2: error: implicit declaration of function 'for_each_matching_node_and_match' [-Werror=implicit-function-declaration]
drivers/clk/samsung/clk.c:252:60: error: expected ';' before '{' token

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

drivers/clk/samsung/clk.c

@@ -284,6 +284,7 @@ void __init samsung_clk_register_gate(struct samsung_gate_clock *list,
  * obtain the clock speed of all external fixed clock sources from device
  * tree and register it
  */
+#ifdef CONFIG_OF
 void __init samsung_clk_of_register_fixed_ext(
 			struct samsung_fixed_rate_clock *fixed_rate_clk,
 			unsigned int nr_fixed_rate_clk,
@@ -300,6 +301,7 @@ void __init samsung_clk_of_register_fixed_ext(
 	}
 	samsung_clk_register_fixed_rate(fixed_rate_clk, nr_fixed_rate_clk);
 }
+#endif
 
 /* utility function to get the rate of a specified clock */
 unsigned long _get_rate(const char *clk_name)