ARM: SPEAr13xx: Add bindings and dt node for misc block

SPEAr SOCs have some miscellaneous registers which are used to configure
peripheral.

This patch adds dt node and binding information for this block.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Cc: devicetree@vger.kernel.org
[viresh: fixed logs/cclist]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>