ACPI: Do not use CONFIG_ACPI_HOTPLUG_MEMORY_MODULE

CONFIG_ACPI_HOTPLUG_MEMORY has been changed to bool (y/n), and
its module option is no longer valid.  So, stop using
CONFIG_ACPI_HOTPLUG_MEMORY_MODULE.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>