ARM: dts: stm32: update i2c2 timing/freq in stm32mp257f-dk

Adjust i2c2 bus rising/falling timing and bus freq to 400KHz
for the stm32mp257f-dk board.

Change-Id: I121119938ffba0ed3f2409952e64cf7c1e37bcb0
Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/u-boot/+/385697
ACI: CIBUILD <MDG-smet-aci-builds@list.st.com>
ACI: CITOOLS <MDG-smet-aci-reviews@list.st.com>
Domain-Review: Amelie DELAUNAY <amelie.delaunay@foss.st.com>
Reviewed-by: Amelie DELAUNAY <amelie.delaunay@foss.st.com>

Author: Alain Volmat

arch/arm/dts/stm32mp257f-dk.dts

@@ -309,9 +309,9 @@
 	pinctrl-names = "default", "sleep";
 	pinctrl-0 = <&i2c2_pins_b>;
 	pinctrl-1 = <&i2c2_sleep_pins_b>;
-	i2c-scl-rising-time-ns = <185>;
-	i2c-scl-falling-time-ns = <20>;
-	clock-frequency = <100000>;
+	i2c-scl-rising-time-ns = <108>;
+	i2c-scl-falling-time-ns = <12>;
+	clock-frequency = <400000>;
 	status = "okay";
 	/* spare dmas for other usage */
 	/delete-property/dmas;