ARM: SPEAr13xx: DT: Add spics gpio controller nodes

SPEAr platform provides a provision to control chipselects of ARM PL022 Prime
Cell spi controller through its system registers, which otherwise remains under
PL022 control which some protocols do not want.

This patch adds spics controller nodes in device tree for various SPEAr13xx
SoCs.

Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Shiraz Hashim <shiraz.hashim@st.com>
Reviewed-by: Vipin Kumar <vipin.kumar@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>