ARM: mach-shmobile: ap4evb: Fix hotplug for SDHI1

On AP4EVB the card detect pin of the top SD/MMC slot is not directly
connected to the tmio/mmcif controller but to a GPIO pin, so polling
needs to be done for SDHI1 and MMCIF in order to support hotplug for
that slot. SHDI1 and MMCIF share that slot, and the used controller
is selected by a DIP switch.
This patch adds a helper function to check if a card is present in that
particular slot, registers this function with SDHI1 and MMCIF and enables
polling for SDHI1.

Signed-off-by: Arnd Hannemann <arnd@arndnet.de>
Tested-by: Yusuke Goda <yusuke.goda.sx@renesas.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>