riscv: dts: add resets property for uart node

Add resets property for uart0 for completeness, although it is
deasserted by default.

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Reviewed-by: Inochi Amaoto <inochiama@outlook.com>
Link: https://lore.kernel.org/r/807f75e433a0f900da40ebb6a448349c98580072.1706577450.git.unicorn_wang@outlook.com
Signed-off-by: Inochi Amaoto <inochiama@outlook.com>

Author: unicornx

arch/riscv/boot/dts/sophgo/sg2042.dtsi

@@ -343,6 +343,7 @@
 			clock-frequency = <500000000>;
 			reg-shift = <2>;
 			reg-io-width = <4>;
+			resets = <&rstgen RST_UART0>;
 			status = "disabled";
 		};
 	};