ASoC: rt5640: Include of.h

of_match_ptr is defined in of.h. Include it explicitly.
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NMark Brown <broonie@linaro.org>

sound/soc/codecs/rt5640.c

@@ -18,6 +18,7 @@
 #include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/regmap.h>
+#include <linux/of.h>
 #include <linux/of_gpio.h>
 #include <linux/platform_device.h>
 #include <linux/spi/spi.h>