Add antirollback clock support

+ /proc/ar_clock stores the antirollback clock, the earliest time_t which
  the kernel will allow itself to be set to.
+ /proc/ar_clock needs to be set only once, at boot. The kernel will
  continually advance it using the jiffies count.

Change-Id: Ifbdb5db7a8e183ffb7b52eb4034411f27f339cf4
5 files changed