ARM: mx28: Let audio support be built by default

Let audio support be built by default.

As sgtl5000 codec is connected via I2C, let MXS I2C driver also be built
by default.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>