clk: wm831x: fix usleep_range with bad range

The delay here is not in atomic context and does not seem critical with
respect to precision, but usleep_range(min,max) with min==max results in
giving the timer subsystem no room to optimize uncritical delays. Fix
this by setting the range to 2000,3000 us.

Fixes: commit f05259a6ffa4 ("clk: wm831x: Add initial WM831x clock driver")
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/clk-wm831x.c

@@ -97,7 +97,8 @@ static int wm831x_fll_prepare(struct clk_hw *hw)
 	if (ret != 0)
 		dev_crit(wm831x->dev, "Failed to enable FLL: %d\n", ret);
 
-	usleep_range(2000, 2000);
+	/* wait 2-3 ms for new frequency taking effect */
+	usleep_range(2000, 3000);
 
 	return ret;
 }