x86: Call idle notifiers

BZ: 35303

Google patched the idle loop for x86-64 (commit 1fd57f722c) and for ARM
(commit 41fa406c26), but they forgot x86-32.

This is preventing their interactive governor from upshifting CPU
frequencies in intel's SOC platforms (e.g. Medfield, etc.).

Fixing that.

NOTE: The notifier calls are not located in the same exact place in the
idle loop for x86-64 and ARM.  The notifier is called inside the
`while(!need_resched)' loop in x86-64 and outside of it in ARM.  Since
Google has likely tuned this governor for ARM, leaving it as in ARM.

Change-Id: Ibefd0c8f08e4b4c24c4a5c32dcdc574f9090b2b9
Signed-off-by: German Monroy <german.monroy@intel.com>