ASoC: dt-bindings: wlf,wm8978: Fix I2C address in example

According to the WM8978 datasheet, the address of the device is fixed as
0011010 in 2-wire mode.

Fixes: 5bd5699c ("ASoC: dt-bindings: Add WM8978 Binding")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/c99fc865e3fca6ea623661c52de7dc6a3c36c8b4.1632487554.git.geert+renesas@glider.be


Signed-off-by: Mark Brown <broonie@kernel.org>