Only emulate fstatfs64 if __NR_fstatfs64 is not defined

Follow-up of e3d6c8bffe79b2c070bc7a3aabc9d9c65f6b099e

Signed-off-by: Eugene Rudoy <gene.devel@gmail.com>
Signed-off-by: Ralf Friedl <Ralf.Friedl@online.de>

libc/misc/statfs/fstatfs64.c

@@ -25,7 +25,7 @@
 #include <sys/syscall.h>
 #include <stddef.h>
 
-#if defined __NR_fstatfs
+#if !defined __NR_fstatfs64
 extern __typeof(fstatfs) __libc_fstatfs;
 
 /* Return information about the filesystem on which FD resides.  */
@@ -55,11 +55,6 @@ int fstatfs64 (int fd, struct statfs64 *buf)
     return 0;
 }
 #else
-/*
- * Use the fstatfs64 system call if fstatfs is not defined
- * This is for backwards compatibility and it should be
- * made default in the future
- */
 int fstatfs64(int fd, struct statfs64 *buf)
 {
 	/* Signature has 2 arguments but syscalls wants 3 */