zenfone8: Add default implementation of fastboot HAL

Change-Id: I54a6f76964cfaaecf4240898c193587167709500
diff --git a/device.mk b/device.mk
index 9c5049e..52359b1 100755
--- a/device.mk
+++ b/device.mk
@@ -98,6 +98,7 @@
 
 # fastbootd
 PRODUCT_PACKAGES += \
+    android.hardware.fastboot@1.0-impl-mock \
     fastbootd
 
 # FM