Add ChangeLog entry for MinGW format specifier fix

Signed-off-by: David Horstmann <[email protected]>

Author: davidhorstmann-arm

ChangeLog.d/fix-mingw-ansi-stdio.txt

@@ -0,0 +1,4 @@
+Bugfix
+  * Fix a build failure with MinGW when the __USE_MINGW_ANSI_STDIO option
+    is set. This was caused by the wrong format specifier being used to
+    print long long values (MBEDTLS_PRINTF_LONGLONG).