Rewrote the bulk of emmc.c to use a standard method of issuing commands that accurately follows HCSS Chapter 3.



git-svn-id: file:///var/johncronin-svn/rpi-boot@69 0f3ef04d-8e58-4d2a-b558-b31704943fbb
Re-implemented 1.8V switch and began work on SDMA support



git-svn-id: file:///var/johncronin-svn/rpi-boot@70 0f3ef04d-8e58-4d2a-b558-b31704943fbb