arm64: tegra: Remove current-speed for SBSA UART

The SBSA UART device tree bindings don't define a current-speed
property, so remove it.
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra234-p3737-0000+p3701-0000.dts

@@ -30,7 +30,6 @@ serial@3100000 {
 		};
 
 		serial@31d0000 {
-			current-speed = <115200>;
 			status = "okay";
 		};
 

arch/arm64/boot/dts/nvidia/tegra234-p3768-0000+p3767-0000.dts

@@ -21,7 +21,6 @@ chosen {
 
 	bus@0 {
 		serial@31d0000 {
-			current-speed = <115200>;
 			status = "okay";
 		};
 

arch/arm64/boot/dts/nvidia/tegra234-p3768-0000.dtsi

@@ -29,7 +29,6 @@ eeprom@57 {
 		};
 
 		serial@31d0000 {
-			current-speed = <115200>;
 			status = "okay";
 		};