Corrections to ChangeLog and Migration guide

This commit fixes typos and re-words
the migration guide. It also adds
the issue number to the ChangeLog.

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/ChangeLog.d/remove-rsa-mode-parameter.txt b/ChangeLog.d/remove-rsa-mode-parameter.txt
index 7ee3adb..b7c6f32 100644
--- a/ChangeLog.d/remove-rsa-mode-parameter.txt
+++ b/ChangeLog.d/remove-rsa-mode-parameter.txt
@@ -3,4 +3,4 @@
      decryption, sign and verify functions are affected. Also
      removes the RNG parameters from the RSA verify functions.
      Existing user code which utilises these RSA functions must
-     remove the mode parameter.
+     remove the mode parameter. Fixes #4278.
diff --git a/docs/3.0-migration-guide.d/remove-rsa-mode-parameter.md b/docs/3.0-migration-guide.d/remove-rsa-mode-parameter.md
index 61100d3..406004f 100644
--- a/docs/3.0-migration-guide.d/remove-rsa-mode-parameter.md
+++ b/docs/3.0-migration-guide.d/remove-rsa-mode-parameter.md
@@ -4,10 +4,13 @@
 This affects all users who use the RSA encryption, decryption, sign and
 verify APIs.
 
-If you were using the mode parameter to specify the wrong mode then
-this behaviour is no longer supported. You must delete the mode
-parameter from your RSA function calls.
-
+You must delete the mode parameter from your RSA function calls.
+Using the correct modes are now the default and only behaviour, and this
+cannot be changed. If you were using the mode parameter to specify the
+wrong mode then this behaviour is no longer supported. For reference the
+correct, supported modes are: Public keys for encryption and verification
+functions and private keys for decryption and signing functions, but the
+user does not have to specify this.
 
 Remove the RNG parameter from RSA functions
 --------------------------------------------
@@ -15,6 +18,6 @@
 This affects all users who use the RSA verify functions.
 
 If you were using the RNG parameters then you must remove
-them from your function calls. Since usiong the wrong mode
+them from your function calls. Since using the wrong mode
 is no longer supported, the RNG parameters namely f_rng
 and p_rng are no longer needed.