intel_telemetry_pltdrv: Silence an uninitialized variable warning

Presumably "pss_period" and "ioss_period" can't both be zero, but this
function is never called so we can't infer that using static analysis
alone.

Silence the warning by setting "ret" to zero.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>