ACPI: NFIT: Install Notify() handler before getting NFIT table

If there is no NFIT at startup, it will return 0 immediately in function
acpi_nfit_add() and will not install Notify() handler. If hotplugging
a nvdimm device later, it will not be identified as there is no Notify()
handler.

Install the handler before getting NFI table in function acpi_nfit_add()
to avoid above issue.

Fixes: dcca12ab

 ("ACPI: NFIT: Install Notify() handler directly")
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>