Improve error message and documents

- fix grammar error
- Add more information for AES_USE_HARDWARE_ONLY
- Improve error message

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/ChangeLog.d/add-aes-hardware-only-option.txt b/ChangeLog.d/add-aes-hardware-only-option.txt
index 2461479..a185aff 100644
--- a/ChangeLog.d/add-aes-hardware-only-option.txt
+++ b/ChangeLog.d/add-aes-hardware-only-option.txt
@@ -2,5 +2,5 @@
    * New configuration option MBEDTLS_AES_USE_HARDWARE_ONLY introduced. When
      using CPU-accelerated AES (e.g., Arm Crypto Extensions), this option
      disables the plain C implementation and the run-time detection for the
-     CPU feature, which reduces code size and avoid the vulnerability of the
+     CPU feature, which reduces code size and avoids the vulnerability of the
      plain C implementation.