Workign eMMC initialization

[jsarrett]

Hello community,

I've got a working implementation of an updated SDMMC driver that supports eMMC. Please feel free to test it out and tell me how it works. It's currently an open pull request on GitHub. https://github.com/espressif/esp-idf/pull/590

I believe it to be correct, but i've only got 1 eMMC chip on hand to test with. and a few other SD cards.

-James