FIH: Re-enable FIH on AN521

1. Define FIH_RET_TYPE macro to avoid defining a function twice with
   different return types.
2. Rename tfm_fih_implementation to tfm_fih.
3. Change all FIH protected functions into FIH format.
4. Expand stack sizes because SPM needs more stack to call FIH function.
   - S_MSP_STACK_SIZE:           2048 -> 2496
   - TFM_NS_AGENT_TZ_STACK_SIZE: 1024 -> 1256

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: Ic0136f0232b1e99940fddcbc57e2898516e9d1fc
23 files changed