x86/mm: Convert update_mmu_cache() and update_mmu_cache_pmd() to functions

Converting macros to functions unhide type problems before
changes will be integrated and trigger problems on other
architectures.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>