ARM: dts: stm32: use exti 19 as main interrupt to support RTC wakeup on stm32mp157

Link between GIC and exti line is now done inside EXTI driver. So in order
to be wake up source exti irqchip has to be used.
Signed-off-by: NAlexandre Torgue <alexandre.torgue@st.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Signed-off-by: NAlexandre Torgue <alexandre.torgue@foss.st.com>

arch/arm/boot/dts/stm32mp151.dtsi

@@ -1560,7 +1560,7 @@
 			reg = <0x5c004000 0x400>;
 			clocks = <&rcc RTCAPB>, <&rcc RTC>;
 			clock-names = "pclk", "rtc_ck";
-			interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
+			interrupts-extended = <&exti 19 IRQ_TYPE_LEVEL_HIGH>;
 			status = "disabled";
 		};