use exact SoC revision instead of wildcard describing
the compatible property requirement in the binding
document. This will make the binding more clearer.

Signed-off-by: Jingchang Lu <b35083@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>