sata_sil: apply MOD15WRITE quirk to TOSHIBA MK2561GSYN

It's a bit odd to see a newer device showing mod15write; however, the
reported behavior is highly consistent and other factors which could
contribute seem to have been verified well enough.  Also, both
sata_sil itself and the drive are fairly outdated at this point making
the risk of this change fairly low.  It is possible, probably likely,
that other drive models in the same family have the same problem;
however, for now, let's just add the specific model which was tested.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: matson <lists-matsonpa@luxsci.me>
References: http://lkml.kernel.org/g/201401211912.s0LJCk7F015058@rs103.luxsci.com
Cc: stable@vger.kernel.org