x86, mm: Create symbolic index into address_markers array

Without this, adding entries into the address_markers array means adding
more and more of an #ifdef maze in pt_dump_init().  By using indices, we
can keep it a bit saner.

Signed-off-by: Andres Salomon <dilinger@queued.net>
LKML-Reference: <201007202219.o6KMJkUs021052@imap1.linux-foundation.org>
Cc: Jordan Crouse <jordan.crouse@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>