unlock: firmware Unlocked sets drive_unlocked=true

The firmware route puts the drive into clear-content mode, so it reports
drive_unlocked=true (and no bus key) per the extended Unlocked contract.

ld/src/lib.rs

@@ -178,6 +178,10 @@ impl Unlocker for LibreDrive {
         Ok(Unlocked {
             vid: Some(vid),
             read_data_key: None,
+            // Firmware unlock puts the drive in clear-content mode: AACS bus
+            // encryption is removed at the drive, so the gate needs no bus key.
+            drive_unlocked: true,
+            read_data_key_err: None,
         })
     }