trusty: arm64-fiq: Re-enable FIQs after restoring cpu state

Make smc call, SMC_FC_FIQ_RESUME, into trusty to re-enable FIQs
after cpu state was lost in idle. The normal psci hooks do not
work for this as they run before Linux has restored its state.

Change-Id: I8a6e47724094ac338455c21a6bfff4e15e92938b
Signed-off-by: Arve Hjønnevåg <arve@android.com>