x86/xen: Redefine XEN_ELFNOTE_INIT_P2M using PUD_SIZE * PTRS_PER_PUD

XEN_ELFNOTE_INIT_P2M has to be 512GB for both 4- and 5-level paging.
(PUD_SIZE * PTRS_PER_PUD) would do this.

Unfortunately, we cannot use P4D_SIZE, which would fit here. With
current headers structure it cannot be used in assembly, if p4d
level is folded.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170716225954.74185-4-kirill.shutemov@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>