Use boot based time for process start time and boot time in /proc

Use boot based time for process start time and boot time in /proc

Commit 411187fb05cd11676b0979d9fbf3291db69dbce2 caused boot time to move and
process start times to become invalid after suspend.  Using boot based time
for those restores the old behaviour and fixes the issue.

[[email protected]: little cleanup]
Signed-off-by: Tomas Janousek <[email protected]>
Cc: Tomas Smetana <[email protected]>
Acked-by: John Stultz <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>