vibrator: switch to external HAL

The vibrator HAL has been moved to
https://github.com/aospm/external_vibrator-ff to allow other devices to
use it.
diff --git a/device-common.mk b/device-common.mk
index d27500d..473d570 100644
--- a/device-common.mk
+++ b/device-common.mk
@@ -183,7 +183,7 @@
 
 # Haptics
 PRODUCT_PACKAGES += \
-    android.hardware.vibrator@1.1-service.sdm845
+    android.hardware.vibrator@1.1-service.ff
 
 # Copy standard platform config files
 PRODUCT_COPY_FILES +=  \