mmc: sdhci: add support nonhotplug

With some devices, SD card could not support hotplug as there is
no cd-gpio, and also could not use polling way due to power
comsumption. So add nonhotplug to meet such requirement and when
SD card lost or removed manually, device will not crash until
next reboot process to detect SD card.

Change-Id: Ie8ea8ec57015f36689a119249003eeaa48391393
Signed-off-by: Guoping Yu <guopingy@codeaurora.org>