Add change log

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/ChangeLog.d/repo-split.txt b/ChangeLog.d/repo-split.txt
new file mode 100644
index 0000000..f03b5ed
--- /dev/null
+++ b/ChangeLog.d/repo-split.txt
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+Changes
+   * Move the crypto part of the library (content of tf-psa-crypto directory)
+     from the Mbed TLS to the TF-PSA-Crypto repository. The crypto code and
+     tests development will now occur in TF-PSA-Crypto, which Mbed TLS
+     references as a Git submodule.