ARM: dts: stm32: use stm32h7 usart compatible string for stm32h743

Previously the FIFO on the stm32h743 usart was not utilized, because
the stm32f7 compatible configures it without FIFO support.

Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32h743.dtsi

@@ -128,7 +128,7 @@
 		};
 
 		usart2: serial@40004400 {
-			compatible = "st,stm32f7-uart";
+			compatible = "st,stm32h7-uart";
 			reg = <0x40004400 0x400>;
 			interrupts = <38>;
 			status = "disabled";
@@ -196,7 +196,7 @@
 		};
 
 		usart1: serial@40011000 {
-			compatible = "st,stm32f7-uart";
+			compatible = "st,stm32h7-uart";
 			reg = <0x40011000 0x400>;
 			interrupts = <37>;
 			status = "disabled";