tf_fuzz: allow specifying policy size in template file

Allow the use of `size <NUM>` in set-policy commands to give a policy a
specific key size (in bits).

For example:

`set policy name myAesPolicy type aes size 2048`

Change-Id: I69febd4107ed1190cf3cc780bf74fd1e02b9e206
Signed-off-by: Nik Dewally <Nik.Dewally@arm.com>
diff --git a/tf_fuzz/tfz-cpp/parser/tf_fuzz_grammar.l b/tf_fuzz/tfz-cpp/parser/tf_fuzz_grammar.l
index 7df9896..c516edc 100644
--- a/tf_fuzz/tfz-cpp/parser/tf_fuzz_grammar.l
+++ b/tf_fuzz/tfz-cpp/parser/tf_fuzz_grammar.l
@@ -120,6 +120,7 @@
 type                      return TYPE;
 algorithm                 return ALG;
 alg                       return ALG;
+size                      return SIZE;
   /* Policy-usage and -lifetime keywords: */
 export                    return EXPORT;
 exp                       return EXPORT;