intel_idle: re-work bxt_idle_state_table_update() and its helper

intel_idle: re-work bxt_idle_state_table_update() and its helper

Orabug: 24810432

Since irtl_ns_units[] has itself zero entries, make sure the caller
recognized those cases along with the MSR read returning zero, as zero
is not a valid value for exit_latency and target_residency.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 3451ab3ebf92b12801878d8b5c94845afd4219f0)
Signed-off-by: Brian Maly <brian.maly@oracle.com>