ACPI/nfit: delete the function to_acpi_nfit_desc

The function to_acpi_nfit_desc and function to_acpi_desc
do the same things,delete the function to_acpi_nfit_desc,
and keep the inline function to_acpi_desc.

Signed-off-by: Xiaochun Lee <lixc17@lenovo.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>