One problem...
from the kernel source
drivers/mmcsd/mmcsd_bus.c
690: sys_mount("/dev/mmcsd/disc0/part1", "/mnt", "vfat", 0xC0ED0000, "iocharset=utf8");
and
drivers/mmcsd/mmcsd_slot_mmsp2.c
589: else sys_mount("/dev/mmcsd/disc0/part1", "/mnt/sd", "vfat", 0xC0ED0000, "iocharset=utf8")...