cxl_pmem.ko uses memory_add_physaddr_to_nid() but ia64 does not export it,
so this causes a build error:

ERROR: modpost: "memory_add_physaddr_to_nid" [drivers/cxl/cxl_pmem.ko] undefined!

Fix this by exporting that function.

Fixes: 8c2676a5 ("hot-add-mem x86_64: memory_add_physaddr_to_nid node fixup")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ben Widawsky <bwidawsk@kernel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: linux-ia64@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Keith Mannthey <kmannth@us.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>