fail to add MMCONFIG information
MMCONFIG is not MMC! AFAIK this error is unrelated. See here: http://lwn.net/Articles/263288/
Don’t you see anything about mmcblk in dmesg? Like here: https://gist.github.com/thomasdziedzic/01482f33aba5971845b3
Booting ISO from iPXE is possible. Search the forums for “ISO” and you should find a lot of information about it.