ARM: DT: STiH407: Add SPI 3 wire and 4 wire pinctrl configs

This patch adds the spi pinctrl configurations for all SPI
controllers, and also the alternate muxings which
can be used depending on board design.

Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>