ARM: STi: DT: STiH407: Add i2c3 alternate pin configs

i2c3 controller can use several sets of pins depending
on board design. This patch adds the missing alternate
pinconfigs.
Signed-off-by: Seraphin Bonnaffe <seraphin.bonnaffe@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>

arch/arm/boot/dts/stih407-pinctrl.dtsi

@@ -430,12 +430,24 @@ st,pins {
 			};
 
 			i2c3 {
-				pinctrl_i2c3_default: i2c3-default {
+				pinctrl_i2c3_default: i2c3-alt1-0 {
 					st,pins {
 						sda = <&pio18 6 ALT1 BIDIR>;
 						scl = <&pio18 5 ALT1 BIDIR>;
 					};
 				};
+				pinctrl_i2c3_alt1_1: i2c3-alt1-1 {
+					st,pins {
+						sda = <&pio17 7 ALT1 BIDIR>;
+						scl = <&pio17 6 ALT1 BIDIR>;
+					};
+				};
+				pinctrl_i2c3_alt3_0: i2c3-alt3-0 {
+					st,pins {
+						sda = <&pio13 6 ALT3 BIDIR>;
+						scl = <&pio13 5 ALT3 BIDIR>;
+					};
+				};
 			};
 
 			spi0 {