anv: Rename clflush_range and state_clflush

anv: Rename clflush_range and state_clflush

It's a bit shorter and easier to work with.  Also, we're about to add a
helper called clflush which does the clflush but without any memory
fencing.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>