ARM: socfpga: Convert to DM serial

Pull the serial port configuration from DT and use DM serial instead
of having the serial configuration in two places, DT and board config.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
diff --git a/arch/arm/dts/socfpga.dtsi b/arch/arm/dts/socfpga.dtsi
index e64127f..3144494 100644
--- a/arch/arm/dts/socfpga.dtsi
+++ b/arch/arm/dts/socfpga.dtsi
@@ -737,6 +737,7 @@
 			reg-shift = <2>;
 			reg-io-width = <4>;
 			clocks = <&l4_sp_clk>;
+			clock-frequency = <100000000>;
 		};
 
 		uart1: serial1@ffc03000 {
@@ -746,6 +747,7 @@
 			reg-shift = <2>;
 			reg-io-width = <4>;
 			clocks = <&l4_sp_clk>;
+			clock-frequency = <100000000>;
 		};
 
 		rst: rstmgr@ffd05000 {