Mark more win32 parameters as unused

Missed one new instance with my last patch.

Bug: 69933068
Test: m native-host-cross
Change-Id: Ib6d0b994131a0011b3a2f1a4633b21756a9d6732
diff --git a/fastboot/fs.cpp b/fastboot/fs.cpp
index 320cf7f..4bf7af8 100644
--- a/fastboot/fs.cpp
+++ b/fastboot/fs.cpp
@@ -185,6 +185,7 @@
     }
     return 0;
 #else
+    UNUSED(fileName, partSize, initial_dir);
     fprintf(stderr, "make_f2fs not supported on Windows\n");
     return -1;
 #endif