libc: fix fstatfs() implementation.

The syscall expects the size of the buffer as the second argument.

Change-Id: I99ede2fec7fcd385ca03ff022c2cffa4297bea8d
diff --git a/libc/include/sys/linux-unistd.h b/libc/include/sys/linux-unistd.h
index 27db2a9..3f151f9 100644
--- a/libc/include/sys/linux-unistd.h
+++ b/libc/include/sys/linux-unistd.h
@@ -87,7 +87,7 @@
 int              fchown (int, uid_t, gid_t);
 void             sync (void);
 int              __fcntl64 (int, int, void *);
-int              fstatfs (int, size_t, struct statfs *);
+int              __fstatfs64 (int, size_t, struct statfs *);
 ssize_t          sendfile (int out_fd, int in_fd, off_t *offset, size_t count);
 int              fstatat (int dirfd, const char *path, struct stat *buf, int flags);
 int              mkdirat (int dirfd, const char *pathname, mode_t mode);