We currently have two issues with the MFC save code:
* save_mfc_decr doesn't handle a transition of 1 -> 0 of the Ds bit
* The Q bit may be stale in the CSA
This change fixes the first issue by clearing the relevant bits from
the MFC_CNTL value in the CSA before or-ing in the updated status.
Also, we add the Q bit to the updated status.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
55d7cd74d4