[vboot] arbitrary kernel physical address (kernel relocation)

[Meulengracht]

One of my wishes for vboot is to properly support kernel relocation. So instead of loading the kernel to a fixed address, we would like to be able to load it to whatever physical address the bootloader just finds. This simplifies things a lot, and as we use PE kernel it should also be PIC enabled by default.

This would enable kernel address randomization.