unexport do_munmap()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

mm/mmap.c

@@ -2125,7 +2125,6 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
 
 	return 0;
 }
-EXPORT_SYMBOL(do_munmap);
 
 int vm_munmap(unsigned long start, size_t len)
 {