Boot: Replace flash partitioning terminology

This change replaces the slot 0/1 terminology with
primary/secondary slot and replaces FLASH_AREA_IMAGE_0/1
with FLASH_AREA_IMAGE_PRIMARY/SECONDARY. This naming
convention fits better to platforms with multiple images
and it is also an architecture agnostic alternative.

Change-Id: I5def429a076024831a702700736d9769a0b2301f
Signed-off-by: David Vincze <david.vincze@arm.com>
diff --git a/docs/user_guides/tfm_user_guide.rst b/docs/user_guides/tfm_user_guide.rst
index 3035400..f653e83 100644
--- a/docs/user_guides/tfm_user_guide.rst
+++ b/docs/user_guides/tfm_user_guide.rst
@@ -62,9 +62,9 @@
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 BL2 bootloader is mandatory to test software update. Furthermore two TF-M blob
 must be built. Outputs of example application and regression test can be used to
-test it. Load output of example application to slot 0 (0x10080000) and output of
-regression test to slot 1 (0x10180000). Add the following line to the end of
-the previous chapter:
+test it. Load output of example application to the primary slot (0x10080000) and
+output of regression test to the secondary slot (0x10180000). Add the following
+line to the end of the previous chapter:
 
 .. code-block:: bash
 
@@ -111,7 +111,7 @@
     [INF] Starting bootloader
     [INF] Image 0: magic=good, copy_done=0xff, image_ok=0xff
     [INF] Scratch: magic=bad, copy_done=0x5, image_ok=0xcf
-    [INF] Boot source: slot 0
+    [INF] Boot source: primary slot
     [INF] Swap type: none
     [INF] Bootloader chainload address offset: 0x80000
     [INF] Jumping to the first image slot
@@ -125,7 +125,7 @@
     [INF] Starting bootloader
     [INF] Image 0: magic=good, copy_done=0xff, image_ok=0xff
     [INF] Scratch: magic=bad, copy_done=0x5, image_ok=0xcf
-    [INF] Boot source: slot 0
+    [INF] Boot source: primary slot
     [INF] Swap type: none
     [INF] Bootloader chainload address offset: 0x80000
     [INF] Jumping to the first image slot
@@ -256,7 +256,7 @@
     [INF] Starting bootloader
     [INF] Image 0: magic=good, copy_done=0xff, image_ok=0xff
     [INF] Scratch: magic=bad, copy_done=0x5, image_ok=0xd9
-    [INF] Boot source: slot 0
+    [INF] Boot source: primary slot
     [INF] Swap type: none
     [INF] Bootloader chainload address offset: 0x20000
     [INF] Jumping to the first image slot
@@ -270,7 +270,7 @@
     [INF] Starting bootloader
     [INF] Image 0: magic=good, copy_done=0xff, image_ok=0xff
     [INF] Scratch: magic=bad, copy_done=0x5, image_ok=0x9
-    [INF] Boot source: slot 0
+    [INF] Boot source: primary slot
     [INF] Swap type: none
     [INF] Bootloader chainload address offset: 0x20000
     [INF] Jumping to the first image slot