MIPS: ralink: Add missing clk_round_rate().

As we dont use the common clock api yet we need to add this stub to allow
building drivers that use the API.
Signed-off-by: NJohn Crispin <john@phrozen.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14900/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/ralink/clk.c

@@ -62,6 +62,12 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
 }
 EXPORT_SYMBOL_GPL(clk_set_rate);
 
+long clk_round_rate(struct clk *clk, unsigned long rate)
+{
+	return -1;
+}
+EXPORT_SYMBOL_GPL(clk_round_rate);
+
 void __init plat_time_init(void)
 {
 	struct clk *clk;