qcacmn: Fix file name tracking logic in QDF nbuf tracker

As WIN has multiple modules and QDF is the last one to be unloaded,
QDF is crashing when it tried to print the file name of an nbuf
allocated by other modules. To fix this, copy the file name in the
QDF nbuf tracker, rather than using the pointer to file name,
to avoid access to the invalid pointer.

CRs-Fixed: 2258770
Change-Id: I27ee76e58b0f5a976840783cfeba451784de85dd

qdf/inc/qdf_mem.h

@@ -86,6 +86,8 @@ void qdf_mem_init(void);
  */
 void qdf_mem_exit(void);
 
+#define QDF_MEM_FILE_NAME_SIZE 48
+
 #ifdef MEMORY_DEBUG
 /**
  * qdf_mem_malloc_debug() - debug version of QDF memory allocation API