pinctrl: SPEAr1310: add register entries for enabling pad direction

Pad direction must also be updated for SPEAr1310, while setting pads values.
This patch adds support for that.

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