dts: arm: socfpga: fix socfpga_de10_nano console

Booting this board failed as the initial console isn't found since
commit c402e8170245 ("dts: arm: socfpga: merge gen5 devicetrees from linux")

The uart0 devicetree entry was missing "clock-frequency = <100000000>:"
since that commit

Fixes: c402e8170245 ("dts: arm: socfpga: merge gen5 devicetrees from linux")
Reported-by: rafael mello <rafaelmello_3@hotmail.com>
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
diff --git a/arch/arm/dts/socfpga_cyclone5_de10_nano.dts b/arch/arm/dts/socfpga_cyclone5_de10_nano.dts
index b620dd8..4be4083 100644
--- a/arch/arm/dts/socfpga_cyclone5_de10_nano.dts
+++ b/arch/arm/dts/socfpga_cyclone5_de10_nano.dts
@@ -77,6 +77,7 @@
 };
 
 &uart0 {
+	clock-frequency = <100000000>;
 	u-boot,dm-pre-reloc;
 };