headers: add WAVEFORMATEXTENSIBLE_IEC61937

This is used for HDMI passthrough [1].

[1] https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ksmedia/ns-ksmedia-waveformatextensible_iec61937

Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-headers/include/ksmedia.h

diff --git a/mingw-w64-headers/include/ksmedia.h b/mingw-w64-headers/include/ksmedia.h
index c3f98a5..10931ec 100644
--- a/mingw-w64-headers/include/ksmedia.h
+++ b/mingw-w64-headers/include/ksmedia.h
@@ -697,6 +697,16 @@
 #define WAVE_FORMAT_EXTENSIBLE			0xFFFE
 #endif
 
+#ifndef _WAVEFORMATEXTENSIBLE_IEC61937_
+#define _WAVEFORMATEXTENSIBLE_IEC61937_
+typedef struct {
+    WAVEFORMATEXTENSIBLE    FormatExt;
+    DWORD                   dwEncodedSamplesPerSec;
+    DWORD                   dwEncodedChannelCount;
+    DWORD                   dwAverageBytesPerSec;
+} WAVEFORMATEXTENSIBLE_IEC61937, *PWAVEFORMATEXTENSIBLE_IEC61937;
+#endif /* _WAVEFORMATEXTENSIBLE_IEC61937_ */
+
 typedef struct {
   ULONG Flags;
   ULONG Control;