Add changelog entry

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
diff --git a/ChangeLog.d/psa-crypto-rename-output-buffer-size-macros.txt b/ChangeLog.d/psa-crypto-rename-output-buffer-size-macros.txt
new file mode 100644
index 0000000..1e8fb5f
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+++ b/ChangeLog.d/psa-crypto-rename-output-buffer-size-macros.txt
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+API changes
+   * Renamed the PSA Crypto API output buffer size macros to bring them in line
+     with version 1.0.0 of the specification.
+
+New deprecations
+   * PSA_KEY_EXPORT_MAX_SIZE, PSA_HASH_SIZE, PSA_MAC_FINAL_SIZE,
+     PSA_BLOCK_CIPHER_BLOCK_SIZE, PSA_MAX_BLOCK_CIPHER_BLOCK_SIZE and
+     PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN have been renamed, and the old names
+     deprecated.