x86: define all _PAGE_* in terms of _PAGE_BIT_* on 64-bit

This patch defines the _PAGE_* paging attributes in pgtable_64.h in terms of
the former defined _PAGE_BIT_* values.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>