ARM: DT: STi: stihxxx-b2120: Add DT nodes for STi audio card

This patch enables the uniperif players 2 & 3 for b2120 boards
and also adds the "simple-audio-card" device node to interconnect
the SoC sound device and the codec.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>