Prefer unsigned types for non-negative numbers

Use size_t for some variables that are array indices.
Use unsigned for some variables that are counts of "small" things.

This is a backport of commit 3c1c8ea3e7.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/main_test.function b/tests/suites/main_test.function
index 8f134ff..1fc76bd 100644
--- a/tests/suites/main_test.function
+++ b/tests/suites/main_test.function
@@ -262,14 +262,15 @@
     const char *default_filename = "TESTCASE_FILENAME";
     const char *test_filename = NULL;
     const char **test_files = NULL;
-    int testfile_count = 0;
+    size_t testfile_count = 0;
     int option_verbose = 0;
 
     /* Other Local variables */
     int arg_index = 1;
     const char *next_arg;
-    int testfile_index, ret, i, cnt;
-    int total_errors = 0, total_tests = 0, total_skipped = 0;
+    size_t testfile_index, i, cnt;
+    int ret;
+    unsigned total_errors = 0, total_tests = 0, total_skipped = 0;
     FILE *file;
     char buf[5000];
     char *params[50];
@@ -347,7 +348,7 @@
           testfile_index < testfile_count;
           testfile_index++ )
     {
-        int unmet_dep_count = 0;
+        size_t unmet_dep_count = 0;
         char *unmet_dependencies[20]; /* only filled when verbose != 0 */
 
         test_filename = test_files[ testfile_index ];
@@ -516,7 +517,7 @@
     else
         mbedtls_fprintf( stdout, "FAILED" );
 
-    mbedtls_fprintf( stdout, " (%d / %d tests (%d skipped))\n",
+    mbedtls_fprintf( stdout, " (%u / %u tests (%u skipped))\n",
              total_tests - total_errors, total_tests, total_skipped );
 
 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C) && \