Document common.h and remove changelog

Added documenttion comments to common.h and removed the changelog
as it is not really necessary for refactoring.

Also modified a comment in aria.c to be clearer

Signed-off-by: Joe Subbiani <joe.subbiani@arm.com>
diff --git a/library/aria.c b/library/aria.c
index a6319d3..f4aa641 100644
--- a/library/aria.c
+++ b/library/aria.c
@@ -385,7 +385,8 @@
  * Big endian 128-bit rotation: r = a ^ (b <<< n), used only in key setup.
  *
  * We chose to store bytes into 32-bit words in little-endian format (see
- * GET/MBEDTLS_PUT_UINT32_LE) so we need to reverse bytes here.
+ * MBEDTLS_GET_UINT32_LE / MBEDTLS_PUT_UINT32_LE ) so we need to reverse
+ * bytes here.
  */
 static void aria_rot128( uint32_t r[4], const uint32_t a[4],
                          const uint32_t b[4], uint8_t n )