[dev][arm_generic_timer] Add suspend hook and supporting routines

On some platforms the state of arm-deneric timer might be lost
in suspend as well as some (deeper) cpu idle related states.
This patch adds routine to export timer state in raw and more
generic form and implements suspend hooks that saves and restores
timer state in per cpu variable across suspend/resume cycle.

Change-Id: I736fa25c933b5814bee8047c36ccb8a68d34060a
2 files changed