portentah7: add log uarts

Author: pennam

variants/arduino_portenta_h7_stm32h747xx_m7/arduino_portenta_h7_stm32h747xx_m7.overlay

@@ -248,6 +248,12 @@
 		zephyr,console = &usart6;
 		zephyr,shell-uart = &usart6;
 		zephyr,cdc-acm-uart0 = &usart6;
+		zephyr,log-uart = &log_uarts;
+	};
+
+	log_uarts: log_uarts {
+		compatible = "zephyr,log-uart";
+		uarts = <&usart6 &board_cdc_acm_uart>;
 	};
 
 	/* used to overcome problems with _C analog pins */