Compile libusb for windows.

Disable the usbdk backend, since all we care about is WinUSB.

Bug: http://b/68993980
Test: mma
Change-Id: If4ab45bbb6de1851c35a464d28a0e4fa6a36aa19
diff --git a/Android.bp b/Android.bp
index 62b575e..d753d50 100644
--- a/Android.bp
+++ b/Android.bp
@@ -76,7 +76,6 @@
                 "libusb/os/poll_windows.c",
                 "libusb/os/threads_windows.c",
                 "libusb/os/windows_nt_common.c",
-                "libusb/os/windows_usbdk.c",
                 "libusb/os/windows_winusb.c",
             ],
 
@@ -85,9 +84,7 @@
             ],
 
             cflags: ["-Werror"],
-
-            // Not working yet.
-            enabled: false,
+            enabled: true,
         },
     },