mmc: dw_mmc: fix suspend/resume operation

This patch is related to re-init processing on suspend/resume.

When card is resuming, some register is reset.  If card is removable,
maybe controller should be rescan for card.  But if assume card is
non-removable, need to restore the old value at registers.

We store the value of FIFOTH at probe time and then restore it in
dw_mci_resume().

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>