Use DUMP_PREFIX_OFFSET when printing hex dumps of corrupt buffers
because modern Linux now prints a 32-bit hash of our 64-bit pointer when
using DUMP_PREFIX_ADDRESS:

00000000b4bb4297: 00 00 00 00 00 00 00 00 3b ee 00 00 00 00 00 00  ........;.......
00000005ec77e26: 00 00 00 00 02 d0 5a 00 00 00 00 00 00 00 00 00  ......Z.........
000000015938018: 21 98 e8 b4 fd de 4c 07 bc ea 3c e5 ae b4 7c 48  !.....L...<...|H

This is totally worthless for a sequential dump since we probably only
care about tracking the buffer offsets and afaik there's no way to
recover the actual pointer from the hashed value.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>