acpi, nfit: fix acpi_get_table leak

Calls to acpi_get_table() must be paired with acpi_put_table() to undo
the mapping established by acpi_tb_acquire_table().

It turns out this has no effect in practice since the NFIT will already
be mapped to support the /sys/firmware/acpi/tables/NFIT attribute in
sysfs.

Fixes: 6b11d1d6 ("ACPI / osl: Remove acpi_get_table_with_size()/early_acpi_os_unmap_memory() users")
Cc: Lv Zheng <lv.zheng@intel.com>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>