PM: Split up sysdev_[suspend|resume] from device_power_[down|up], fix

Impact: module build fix

Fix:

 ERROR: "sysdev_resume" [arch/x86/kernel/apm.ko] undefined!
 ERROR: "sysdev_suspend" [arch/x86/kernel/apm.ko] undefined!

As these APIs are now used by the APM driver, which can be built
as a module.

Also fix a few extra (and inconsistent) newlines in comment blocks
preceding these functions.

Signed-off-by: Ingo Molnar <mingo@elte.hu>