kvm tools: Fix alignment for mpf_intel table

Thomas and Asias reported that kernel doesn't find MP
tables on 32 bit host. This is because previously the
alignment was done on address obtained from calloc
missing the fact that MP tables are put into guest
memory *with* offset and MP signature should be
calculated keeping this offset in midn as well and
then aligned.

Reported-by: Thomas Heil <heil@terminal-consulting.de>
Reported-by: Asias He <asias.hejun@gmail.com>
Tested-by: Thomas Heil <heil@terminal-consulting.de>
Tested-by: Asias He <asias.hejun@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>