arch/x86: unify pte_to_pgoff and pgoff_to_pte helpers

arch/x86: unify pte_to_pgoff and pgoff_to_pte helpers

Use unified pte_bitop helper to manipulate bits in pte/pgoff bitfield, and
convert pte_to_pgoff/pgoff_to_pte to inlines.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>