rockchip: clk: rk3368: mark 'priv' __maybe_unused in rk3368_clk_set_rate()

With the clock support in rk3368_clk_set_rate() conditionalized on
various feature definitions, 'priv' can remain unused (e.g. in the
SPL build when only MMC is enabled).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/clk/rockchip/clk_rk3368.c

@@ -353,7 +353,7 @@ static ulong rk3368_gmac_set_clk(struct rk3368_cru *cru,
 
 static ulong rk3368_clk_set_rate(struct clk *clk, ulong rate)
 {
-	struct rk3368_clk_priv *priv = dev_get_priv(clk->dev);
+	__maybe_unused struct rk3368_clk_priv *priv = dev_get_priv(clk->dev);
 	ulong ret = 0;
 
 	debug("%s id:%ld rate:%ld\n", __func__, clk->id, rate);