mmc: vt8500: Add support for vt8500 sd host controller

Hi Chris,

I posted a patch to add support for this host controller a few weeks ago, and resent it a few weeks after that. Other than some minor code fixup requests (which I've changed), I haven't heard a peep from anyone.

Patch at:
https://patchwork.kernel.org/patch/1654541/

Regards
Tony Prisk