Remove unnecessary parameter in MPS reader unit test

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/tests/suites/test_suite_mps.data b/tests/suites/test_suite_mps.data
index 158302b..f25d703 100644
--- a/tests/suites/test_suite_mps.data
+++ b/tests/suites/test_suite_mps.data
@@ -119,4 +119,4 @@
 mbedtls_reader_inconsistent_usage:8
 
 MPS Reader: Feed with invalid buffer (NULL)
-mbedtls_mps_reader_feed_empty:0
+mbedtls_mps_reader_feed_empty:
diff --git a/tests/suites/test_suite_mps.function b/tests/suites/test_suite_mps.function
index 30e65d4..d67e7d2 100644
--- a/tests/suites/test_suite_mps.function
+++ b/tests/suites/test_suite_mps.function
@@ -1073,7 +1073,7 @@
 /* END_CASE */
 
 /* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
-void mbedtls_mps_reader_feed_empty( int option )
+void mbedtls_mps_reader_feed_empty()
 {
     /* This test exercises the behaviour of the reader when it is
      * fed with a NULL buffer. */
@@ -1085,17 +1085,10 @@
 
     /* Preparation (lower layer) */
     mbedtls_mps_reader_init( &rd, NULL, 0 );
-    switch( option )
-    {
-        case 0: /* NULL buffer */
-            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, NULL, sizeof( buf ) ) ==
-                         MBEDTLS_ERR_MPS_READER_INVALID_ARG );
-            break;
 
-        default:
-            TEST_ASSERT( 0 );
-            break;
-    }
+    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, NULL, sizeof( buf ) ) ==
+                 MBEDTLS_ERR_MPS_READER_INVALID_ARG );
+
     /* Subsequent feed-calls should still succeed. */
     TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );