headers: Add CacheUnknown in winnt.h

Required for https://github.com/google/benchmark/commit/24e0bd82

Signed-off-by: Biswapriyo Nath <nathbappai@gmail.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-headers/include/winnt.h

diff --git a/mingw-w64-headers/include/winnt.h b/mingw-w64-headers/include/winnt.h
index 666f260..5179840 100644
--- a/mingw-w64-headers/include/winnt.h
+++ b/mingw-w64-headers/include/winnt.h
@@ -5359,7 +5359,7 @@
 #define LTP_PC_SMT 0x1
 
     typedef enum _PROCESSOR_CACHE_TYPE {
-      CacheUnified,CacheInstruction,CacheData,CacheTrace
+      CacheUnified,CacheInstruction,CacheData,CacheTrace,CacheUnknown
     } PROCESSOR_CACHE_TYPE;
 
 #define CACHE_FULLY_ASSOCIATIVE 0xFF