Support 'fastboot getvar unlocked' command.

Test: fastboot getvar unlocked.
Bug: 78793464

Change-Id: Ie59c6db90a503e9a6e9ac1c416e4ee5deac60479
diff --git a/fastboot/device/utility.h b/fastboot/device/utility.h
index 4f0d079..bb08f72 100644
--- a/fastboot/device/utility.h
+++ b/fastboot/device/utility.h
@@ -58,3 +58,4 @@
 bool OpenPartition(FastbootDevice* device, const std::string& name, PartitionHandle* handle);
 bool GetSlotNumber(const std::string& slot, android::hardware::boot::V1_0::Slot* number);
 std::vector<std::string> ListPartitions(FastbootDevice* device);
+bool GetDeviceLockStatus();