ASoC: Add basic WM8918 support

The WM8918 is register compatible with the WM8904 with a subset of the
functionality. Add the device ID, a subsequent patch will ensure that only
the relevant functionality is exported to userspace.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>

sound/soc/codecs/wm8904.c

diff --git a/sound/soc/codecs/wm8904.c b/sound/soc/codecs/wm8904.c
index 9b3bba4..b085575 100644
--- a/sound/soc/codecs/wm8904.c
+++ b/sound/soc/codecs/wm8904.c
@@ -2560,6 +2560,7 @@
 static const struct i2c_device_id wm8904_i2c_id[] = {
 	{ "wm8904", WM8904 },
 	{ "wm8912", WM8912 },
+	{ "wm8918", WM8904 },   /* Actually a subset, updates to follow */
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, wm8904_i2c_id);