fix code style and comment issues

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/aesce.c b/library/aesce.c
index e47665a..ee0c8e1 100644
--- a/library/aesce.c
+++ b/library/aesce.c
@@ -60,7 +60,7 @@
     return (auxval & (HWCAP_ASIMD | HWCAP_AES)) ==
            (HWCAP_ASIMD | HWCAP_AES);
 #else
-    /* Suppose aes instructions are supported. */
+    /* Assume AES instructions are supported. */
     return 1;
 #endif
 }
@@ -143,7 +143,6 @@
     return 0;
 }
 
-
 /*
  * Compute decryption round keys from encryption round keys
  */
@@ -244,8 +243,10 @@
         case 128:
         case 192:
         case 256:
-            aesce_setkey_enc(rk, key, bits); break;
-        default: return MBEDTLS_ERR_AES_INVALID_KEY_LENGTH;
+            aesce_setkey_enc(rk, key, bits);
+            break;
+        default:
+            return MBEDTLS_ERR_AES_INVALID_KEY_LENGTH;
     }
 
     return 0;
diff --git a/library/aesce.h b/library/aesce.h
index 0d6d09e..1e72e5b 100644
--- a/library/aesce.h
+++ b/library/aesce.h
@@ -64,7 +64,6 @@
                             const unsigned char input[16],
                             unsigned char output[16]);
 
-
 /**
  * \brief           Internal round key inversion. This function computes
  *                  decryption round keys from the encryption round keys.