XQuartz: Fix the new ProcAppleDRIDestroyPixmap code REQUEST_SIZE_MATCH.

It had a copy and paste mistake that I didn't notice. :/
It was using the CreatePixmapReq.

Also add a missing B16 to the end of the length for the DestroyPixmapReq struct.

Now the AppleDRIDestroyPixmap request seem to work.
(cherry picked from commit 295fe25bd8fa2d141291a9d9b6ef7b75fcccb4dd)

hw/xquartz/xpr/appledristr.h

@@ -226,7 +226,7 @@ typedef struct {
 typedef struct {
     CARD8 reqType; /*1*/
     CARD8 driReqType; /*2*/
-    CARD16 length; /*4*/
+    CARD16 length B16; /*4*/
     CARD32 drawable B32; /*8*/
 } xAppleDRIDestroyPixmapReq;