btmon: Suppress HCI vendor events

When idle, Marvell 88W8897 Bluetooth adapter fills btmon logs with:

> HCI Event: Vendor (0xff) plen 5                    [hci0] 0.300944
        05 80 00 09 00

Suppress these events with the new -V option.
https://gfiber-internal-review.googlesource.com/#/c/83000/

Change-Id: Ie2d1177abca30ddfa0df1a92cf617fa315fc3ea5
diff --git a/package/bluez_utils/S54bluez b/package/bluez_utils/S54bluez
index c1df5b3..a520d81 100755
--- a/package/bluez_utils/S54bluez
+++ b/package/bluez_utils/S54bluez
@@ -85,7 +85,7 @@
       fi
 
       echo "$0: Starting btmon"
-      babysit 30 btmon -A -t 2>&1 | logos btmon &
+      babysit 30 btmon -A -V -t 2>&1 | logos btmon &
       sleep 1
 
       echo "$0: Starting bluetoothd"