[IA64] Fix format warning in arch/ia64/kernel/acpi.c

arch/ia64/kernel/acpi.c:481: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long unsigned int’

Introduced by commit 05f2f274
    [IA64] Avoid array overflow if there are too many cpus in SRAT table

Signed-off-by: Tony Luck <tony.luck@intel.com>