x86: merge mmu_context.h

Impact: cleanup

tj: * changed cpu to unsigned as was done on mmu_context_64.h as cpu
      id is officially unsigned int
    * added missing ';' to 32bit version of deactivate_mm()

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>