ASoC: wm_adsp: Use usleep_range for short delay

Replace the 1ms msleep in wm_adsp2_ena with a usleep_range, as per
normal guidance on delay functions. Also tighten up the delay a little
as 1ms was quite generous.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/codecs/wm_adsp.c b/sound/soc/codecs/wm_adsp.c
index 24485ec..4188c37 100644
--- a/sound/soc/codecs/wm_adsp.c
+++ b/sound/soc/codecs/wm_adsp.c
@@ -2237,7 +2237,7 @@
 		if (val & ADSP2_RAM_RDY)
 			break;
 
-		msleep(1);
+		usleep_range(250, 500);
 	}
 
 	if (!(val & ADSP2_RAM_RDY)) {