eeepc-laptop: don't assume get_acpi succeeds

In eeepc_hotk_thaw, we assume that get_acpi() will effectively return a
bool. However, it is possible that get_acpi() returns an error instead.
We should not be writing error values to the ACPI device, even though
it's quite possible that we couldn't contact the ACPI device in the
first place.

Signed-off-by: Frans Klaver <fransklaver@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>