pinctrl: st: add pinctrl support for the STiH407 SoC

This patch adds the initial support for pinctrl based on H407 SoC.

Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>