SPM: Add build config for IPC-only FF-M APIs

Use macro "CONFIG_TFM_SPM_BACKEND_IPC" to control FF-M APIs
and SPM APIs that are only used by IPC backend:
- psa_get()
- psa_reply()
- spm_get_handle_by_signal()

Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
Change-Id: I86a7679a325e72ee9eaa7c323cb6965a27975ae3
4 files changed