Simplify Input usage macros

Also ensure they are used in test data rather than values

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/tests/suites/test_suite_pkcs12.function b/tests/suites/test_suite_pkcs12.function
index 3d402d7..81324ed 100644
--- a/tests/suites/test_suite_pkcs12.function
+++ b/tests/suites/test_suite_pkcs12.function
@@ -5,7 +5,6 @@
 {
    USE_NULL_INPUT = 0,
    USE_GIVEN_INPUT = 1,
-   USE_NULL_INPUT_WITH_SIZE = 2,
 } input_usage_method_t;
 
 /* END_HEADER */
@@ -32,24 +31,14 @@
    size_t key_size = key_size_arg;
 
    if( password_usage == USE_GIVEN_INPUT )
-   {
       password = password_arg->x;
-      password_len = password_arg->len;
-   }
-   else if( password_usage == USE_NULL_INPUT_WITH_SIZE )
-   {
-      password_len = password_arg->len;
-   }
+
+   password_len = password_arg->len;
 
    if( salt_usage == USE_GIVEN_INPUT )
-   {
       salt = salt_arg->x;
-      salt_len = salt_arg->len;
-   }
-   else if( salt_usage == USE_NULL_INPUT_WITH_SIZE )
-   {
-      salt_len = salt_arg->len;
-   }
+
+   salt_len = salt_arg->len;
 
    ASSERT_ALLOC( output_data, key_size );