tboot: Add return values for tboot_sleep

.. as appropiately. As tboot_sleep now returns values.
remove tboot_sleep_wrapper.

Suggested-and-Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Joseph Cihula <joseph.cihula@intel.com>
[v1: Return -1/0/+1 instead of ACPI_xx values]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>