ARM diagnostic register across suspend/resume

[Shawn Guo]

Hi Will, Catalin,

The CP15 diagnostic register holds some bits for ARM errata workaround.
Since core gets power gated across suspend/resume cycle, these bits will
get lost along the way.  Is it okay for errata workaround to continue
working after suspend, or do we have to save/restore diagnostic register
to keep workaround effective?

Shawn