Move ftime to a compatibility symbol

It was made deprecated on 2.31, so it moves to compat symbol after
two releases.  It was also removed from exported symbol for riscv32
(since ABI will be supported on for 2.33).

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Lukasz Majewski <lukma@denx.de>