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

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

Signed-off-by: ganghe <[email protected]>

Author: ganghe

boards/sifli/sf32lb52_devkit_lcd/sf32lb52_devkit_lcd.dts

@@ -19,6 +19,7 @@
 		zephyr,code-partition = &code;
 		zephyr,console = &usart1;
 		zephyr,shell-uart = &usart1;
+        zephyr,bt-hci = &mbox;        
 	};
 };