powercap: idle_inject: Replace play_idle() with play_idle_precise() in comments

After commit 333cff6c ("powercap/drivers/idle_inject: Specify
idle state max latency"), we convert to use play_idle_precise() with
max allowed latency to specify the idle state.

Some function comments still use play_idle(), let's update it to
play_idle_precise().

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Frank Lee <frank@allwinnertech.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>