[IA64] mca.c: Fix cast from integer to pointer warning

ia64_mca_cpu_init has a void *data local variable that is assigned
the value from either __get_free_pages() or mca_bootmem(). The problem
is that __get_free_pages returns an unsigned long and mca_bootmem, via
alloc_bootmem(), returns a void *. format_mca_init_stack takes the void *,
and it's also used with __pa(), but that casts it to long anyway.

This results in the following build warning:

arch/ia64/kernel/mca.c:1898: warning: assignment makes pointer from
integer without a cast

Cast the return of __get_free_pages to a void * to avoid
the warning.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>