PM / core: Split dpm_suspend_noirq() and dpm_resume_noirq()

Put the device interrupts disabling and enabling as well as
cpuidle_pause() and cpuidle_resume() called during the "noirq"
stages of system suspend into separate functions to allow the
core suspend-to-idle code to be optimized (later).

The only functional difference this makes is that debug facilities
and diagnostic tools will not include the above operations into the
"noirq" device suspend/resume duration measurements.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>