ARM: dts: igep00x0: Add pinmux configuration for MCBSP2

Add pinmux configuration for MCBSP2 connected to the TDM interface.
With this configuration the Headset modules works as expected.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Acked-by: Javier Martinez Canillas <javier@dowhile0.org>
Signed-off-by: Benoit Cousson <bcousson@baylibre.com>