Misc changes:

 - Unexport various PAT primitives

 - Unexport per-CPU tlbstate

 - Provide an opt-in (prctl driven) mechanism to flush the L1D cache on context switch.
   The goal is to allow tasks that are paranoid due to the recent snoop assisted data
   sampling vulnerabilites, to flush their L1D on being switched out.
   This protects their data from being snooped or leaked via side channels
   after the task has context switched out.

Signed-off-by: Ingo Molnar <mingo@kernel.org>