ARM: integrator: add MMCI device to IM-PD1

The IM-PD1 logic module daughterboard holds an MMCI block, which
we can now provide using platform resources such as proper GPIO
lines etc. We add the GPIO table dynamically and using the new
GPIO descriptor mechanism. Tested and hey, it works:

root@integrator:/ mount /dev/mmcblk0p1 /mnt/
root@integrator:/ ls /mnt/
ARM          U-BOOT.EXE   u-boot.bin   u-boot.srec  u-pad.bin

Reviewed-by: Alexandre Courbot <gnurou@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>