SPM: Rename 'spm/common' into 'spm/ffm'

The name 'common' confused a bit, as its real purpose is for general
FF-M API implementation. Rename this folder as the first step for
re-structure patches.

There are some 'common' folder legacies still in the renamed 'ffm'
folder. They will be updated in the following patches.

Change-Id: Ic72fcf9ecf47f2185a82761edfdcbcd3c4569421
Signed-off-by: Ken Liu <Ken.Liu@arm.com>
diff --git a/docs/contributing/code_review_guide.rst b/docs/contributing/code_review_guide.rst
index e9470e6..8bbf33a 100644
--- a/docs/contributing/code_review_guide.rst
+++ b/docs/contributing/code_review_guide.rst
@@ -78,7 +78,7 @@
 
 .. code-block:: c
 
-  /* R3.1 FILE: s/spm/common/psa_client.c */
+  /* R3.1 FILE: s/spm/ffm/psa_client.c */
 
   /* R3.2 FILE: s/spm/cmsis_psa/tfm_secure_context.c */
 
@@ -86,10 +86,10 @@
 
   /* R3.4 FILE: s/spm/cmsis_psa/main.c, 'main' is a good entry name. */
   void main(void);
-  /* R3.4 FILE: s/spm/common/spm.c, 'spm\_' as the namespace */
+  /* R3.4 FILE: s/spm/ffm/spm.c, 'spm\_' as the namespace */
   void spm_init(void);
 
-  /* R3.5 FILE: s/spm/common/main.c */
+  /* R3.5 FILE: s/spm/ffm/main.c */
   static void init_functions(void);
 
   /* R3.6 Not permitted: */
@@ -105,7 +105,7 @@
     external MACRO wrapped assembler code is allowed. Here is one example of the
     logic folder:
 
-    - 'secure_fw/spm/common'.
+    - 'secure_fw/spm/ffm'.
 
 Examples:
 
@@ -113,7 +113,7 @@
 
   /*
    * R4.1 The following MACRO is allowed to be referenced under
-   * 'secure_fw/spm/common'
+   * 'secure_fw/spm/ffm'
    */
   #define SVC(code) __asm volatile("svc  %0", ::"I"(code))
 
diff --git a/docs/design_documents/source_structure.rst b/docs/design_documents/source_structure.rst
index 208c7bf..a549bf7 100644
--- a/docs/design_documents/source_structure.rst
+++ b/docs/design_documents/source_structure.rst
@@ -145,7 +145,7 @@
 Folder name                         Purpose
 =================================== ===========================================
 include/\*                          SPM public headers.
-common/\*                           SPM common logic complies with PSA-FF-M and
+ffm/\*                              SPM logic complies with PSA-FF-M and
                                     its necessary supporting functionalities,
                                     such as the runtime API and the thread
                                     operation, etc.