PS: Introduce option to read old persistent format

Because the format of the object table in persistent storage was changed
(see commit 296ebb4f5965 "PS: Make PS crypto less stateful"), a new
configuration option PS_SUPPORT_FORMAT_TRANSITION is added that supports
reading the previous format. The new format will be used when writing.

Signed-off-by: Chris Brand <chris.brand@cypress.com>
Change-Id: I8eb27cc0d1be2cd2326d66cd964b90d9909129bf
diff --git a/docs/configuration/index.rst b/docs/configuration/index.rst
index 6783685..520f91f 100644
--- a/docs/configuration/index.rst
+++ b/docs/configuration/index.rst
@@ -200,6 +200,8 @@
 +---------------------------------------+-----------+-----------------+
 |PS_ENCRYPTION                          | Build     |   ON            |
 +---------------------------------------+-----------+-----------------+
+|PS_SUPPORT_FORMAT_TRANSITION           | Build     |   OFF           |
++---------------------------------------+-----------+-----------------+
 |PS_CRYPTO_AEAD_ALG                     | Build     |   PSA_ALG_GCM   |
 +---------------------------------------+-----------+-----------------+
 |PS_CREATE_FLASH_LAYOUT                 | Component |   1             |