ARM: dts: stm32: limit sdio frequency to 14Mhz for stm32f429i-eval

This avoids the following errors while reading on mmc:
  Read data bytes CRC error: 0x2
  switch to partitions #0, OK
  mmc0 is current device
  Read data bytes CRC error: 0x82002
  ** Unrecognized filesystem type **
Signed-off-by: NPatrice Chotard <patrice.chotard@st.com>

arch/arm/dts/stm32429i-eval.dts

@@ -230,6 +230,7 @@
 	pinctrl-0 = <&sdio_pins>;
 	pinctrl-1 = <&sdio_pins_od>;
 	bus-width = <4>;
+	max-frequency = <14000000>;
 };
 
 &timers1 {