tools/power turbostat: fix file descriptor leaks

Fix file descriptor leaks by closing fp before return.

Addresses-Coverity-ID: 1444591 ("Resource leak")
Addresses-Coverity-ID: 1444592 ("Resource leak")
Fixes: 5ea7647b

 ("tools/power turbostat: Warn on bad ACPI LPIT data")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>