mmc: remove MMC bus legacy suspend/resume method

MMC bus is using legacy suspend/resume method, which is not compatible if
runtime pm callbacks are used. In this scenario, MMC bus suspend/resume
callbacks cannot be called when system entering S3. So change to use the
new defined dev_pm_ops for system sleeping mode.

Tested on AM335x Platform. Solves major issue/crash reported at
http://www.mail-archive.com/linux-omap@vger.kernel.org/msg65425.html

Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Tested-by: Hebbar, Gururaja <gururaja.hebbar@ti.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Ulf Hansson <ulf.hansson@stericsson.com>
Signed-off-by: Chris Ball <cjb@laptop.org>