board: sifli: sf32lb52_devkit_lcd: Add mbox in board device tree

Add mailbox in board devicetree, used in Bluetooth HCI driver.

Signed-off-by: Gang He <[email protected]>

Author: ganghe

boards/sifli/sf32lb52_devkit_lcd/sf32lb52_devkit_lcd.dts

@@ -21,6 +21,7 @@
 		zephyr,code-partition = &code;
 		zephyr,console = &usart1;
 		zephyr,shell-uart = &usart1;
+		zephyr,bt-hci = &mbox;
 	};
 
 	buttons {