Use correct test case conditionals for helper functions in tests/suites

Fix unused-function errors.

Signed-off-by: Michael Schuster <michael@schuster.ms>
diff --git a/tests/suites/test_suite_entropy.function b/tests/suites/test_suite_entropy.function
index c89c26c..a4f3b1b 100644
--- a/tests/suites/test_suite_entropy.function
+++ b/tests/suites/test_suite_entropy.function
@@ -60,6 +60,8 @@
 }
 
 #if defined(MBEDTLS_ENTROPY_NV_SEED)
+
+#if defined(MBEDTLS_MD_LIGHT) && defined(MBEDTLS_PLATFORM_NV_SEED_ALT)
 /*
  * NV seed read/write functions that use a buffer instead of a file
  */
@@ -84,7 +86,9 @@
     memcpy(buffer_seed, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);
     return 0;
 }
+#endif /* MBEDTLS_MD_LIGHT && MBEDTLS_PLATFORM_NV_SEED_ALT */
 
+#if defined(MBEDTLS_FS_IO)
 /*
  * NV seed read/write helpers that fill the base seedfile
  */
@@ -111,6 +115,7 @@
     return 0;
 }
 
+#if defined(MBEDTLS_PLATFORM_NV_SEED_ALT)
 static int read_nv_seed(unsigned char *buf, size_t buf_len)
 {
     FILE *f;
@@ -133,6 +138,8 @@
 
     return 0;
 }
+#endif /* MBEDTLS_PLATFORM_NV_SEED_ALT */
+#endif /* MBEDTLS_FS_IO */
 #endif /* MBEDTLS_ENTROPY_NV_SEED */
 /* END_HEADER */