mmc: dw_mmc: use dev_pm_ops for dw_mmc controllers

This patch modifies dw_mmc to use dev_pm_ops.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>