x86: PM: Make APM idle driver initialize polling state

x86: PM: Make APM idle driver initialize polling state

Update the APM driver overlooked by commit 1b39e3f813b4 (cpuidle: Make
drivers initialize polling state) to initialize the polling state like
the other cpuidle drivers modified by that commit to prevent cpuidle
from crashing.

Fixes: 1b39e3f813b4 (cpuidle: Make drivers initialize polling state)
Reported-by: Ville Syrjälä <[email protected]>
Tested-by: Ville Syrjälä <[email protected]>
Cc: 4.14+ <[email protected]> # 4.14+
Signed-off-by: Rafael J. Wysocki <[email protected]>