Legacy here means pdc4030, ali14xx, umc8672, dtc2278, ht6560b and qd65xx.
They cannot be probed and initialized at a boot parameters' parsing time,
because probing code depends on not yet ready kernel subsystems.

This change also fixes boot parameters' ordering issue, fe. you could
pass "ide0=dtc2278 ide0=noautotune" and "noautotune" was catched too late.