Add MBEDTLS_FS_IO guard on default NV seed defines in platform.h
The default implementation won't work without MBEDTLS_FS_IO, so
leave undefined otherwise.
diff --git a/include/mbedtls/platform.h b/include/mbedtls/platform.h
index 10137d7..5fa01b5 100644
--- a/include/mbedtls/platform.h
+++ b/include/mbedtls/platform.h
@@ -76,6 +76,7 @@
#if !defined(MBEDTLS_PLATFORM_STD_EXIT_FAILURE)
#define MBEDTLS_PLATFORM_STD_EXIT_FAILURE EXIT_FAILURE /**< Default exit value to use */
#endif
+#if defined(MBEDTLS_FS_IO)
#if !defined(MBEDTLS_PLATFORM_STD_NV_SEED_READ)
#define MBEDTLS_PLATFORM_STD_NV_SEED_READ mbedtls_platform_std_nv_seed_read
#endif
@@ -85,6 +86,7 @@
#if !defined(MBEDTLS_PLATFORM_STD_NV_SEED_FILE)
#define MBEDTLS_PLATFORM_STD_NV_SEED_FILE "seedfile"
#endif
+#endif /* MBEDTLS_FS_IO */
#else /* MBEDTLS_PLATFORM_NO_STD_FUNCTIONS */
#if defined(MBEDTLS_PLATFORM_STD_MEM_HDR)
#include MBEDTLS_PLATFORM_STD_MEM_HDR