xen/arm: Print whether Xen is booting using ACPI or DT

Make it easier to figure out whether Xen is booting using ACPI or DT by
printing a message on the console.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/setup.c

@@ -753,6 +753,11 @@ void __init start_xen(unsigned long boot_phys_offset,
     /* Parse the ACPI tables for possible boot-time configuration */
     acpi_boot_table_init();
 
+    if ( acpi_disabled )
+        printk("Booting using Device Tree\n");
+    else
+        printk("Booting using ACPI\n");
+
     end_boot_allocator();
 
     vm_init();