x86/pvops: replace arch_enter_lazy_cpu_mode with arch_start_context_switch

Impact: simplification, prepare for later changes

Make lazy cpu mode more specific to context switching, so that
it makes sense to do more context-switch specific things in
the callbacks.

Signed-off-by: Jeremy Fitzhardinge <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
8 files changed