blackfin: fixing warning by including proper headers

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
diff --git a/arch/blackfin/lib/clocks.c b/arch/blackfin/lib/clocks.c
index 97795e1..7ed56a7 100644
--- a/arch/blackfin/lib/clocks.c
+++ b/arch/blackfin/lib/clocks.c
@@ -36,7 +36,10 @@
 u_long get_cclk(void)
 {
 	static u_long cached_cclk_pll_div, cached_cclk;
-	u_long div, csel, ssel;
+	u_long div, csel;
+#ifndef CGU_DIV
+	u_long ssel;
+#endif
 
 	if (pll_is_bypassed())
 		return CONFIG_CLKIN_HZ;