Core: Move library model SPM code to 'spm' folder

- Move the library SPM APIs from 'core' to 'spm' folder, put them
  into file 'spm_func.c'. Also move function declaration to the
  'spm' header file.
- Change the API names with 'tfm_spm' prefix.
- Remove inclusion of some unused header files.

Change-Id: If7ec1347cbf0d6d19bcb74bbb84f48f15c18cec9
Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
diff --git a/docs/design_documents/enum_implicit_casting.rst b/docs/design_documents/enum_implicit_casting.rst
index d6194c7..2d47520 100644
--- a/docs/design_documents/enum_implicit_casting.rst
+++ b/docs/design_documents/enum_implicit_casting.rst
@@ -143,8 +143,8 @@
   * ``int32_t tfm_return_from_partition``
   * ``int32_t tfm_check_sfn_req_integrity``
   * ``int32_t tfm_core_check_sfn_req_rules``
-  * ``int32_t tfm_core_sfn_request_handler``
-  * ``int32_t tfm_core_sfn_request_thread_mode``
+  * ``int32_t tfm_spm_sfn_request_handler``
+  * ``int32_t tfm_spm_sfn_request_thread_mode``
 * ``enum tfm_buffer_share_region_e``: the following function prototypes will be
   changed:
 
@@ -187,5 +187,5 @@
 --------------
 
 
-*Copyright (c) 2019, Arm Limited. All rights reserved.*
+*Copyright (c) 2019-2020, Arm Limited. All rights reserved.*