Reword ChangeLog entry. Specifically:

* Fix a grammatical typo
* Mention shared memory
* Mention overlap support in the security section
* Improve wording

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/ChangeLog.d/psa-shared-memory-protection.txt b/ChangeLog.d/psa-shared-memory-protection.txt
index a158ae8..765c97c 100644
--- a/ChangeLog.d/psa-shared-memory-protection.txt
+++ b/ChangeLog.d/psa-shared-memory-protection.txt
@@ -6,9 +6,12 @@
      by copying buffers.
      This feature increases code size and memory usage. If buffers passed to
      PSA functions are owned exclusively by the PSA core for the duration of
-     the function call, copying may be disabled by setting
+     the function call (i.e. no buffer parameters are stored in memory shared
+     with an untrusted party), copying may be disabled by setting
      MBEDTLS_PSA_ASSUME_EXCLUSIVE_BUFFERS.
+     Note that setting this option will cause input-output buffer overlap to
+     be only partially supported.
 Bugfix
    * Fully support arbitrary overlap between inputs and outputs of PSA
-     functions. Note that overlap is only partial supported when
+     functions. Note that overlap is still only partially supported when
      MBEDTLS_PSA_ASSUME_EXCLUSIVE_BUFFERS is set.