Reduce the AOSP reserved range for vendor-specific events

The code 0x51 conflicts with this range (already reserved by partner).

Bug: 360924438
Bug: 360925496
Test: mma -j32
Flag: com.android.bluetooth.flags.hci_vendor_specific_extension
Change-Id: I542e000c08bf32f654c5afb9f1602cf41fac9c0f