Blender Git Loki

Cycles: Revert all host update specific changes

The approach didn't turn out to be that useful after all as there
are unavoidable dependencies of data from the device. For example,
to know whether object intersects volume or not it is required to
run displacement kernels.

The way of splitting host and device updates caused state where
some data is not yet available, causing confusion and leaving
code to be error-prone.