Fix build breakage for non-CR50 builds.

Commit ae8d044cd1 introduced a externally
defined callback _plat__ResetCallback()
which is not available outside the CR50
environment.

Address the issue with conditional compilation.

TEST=docker fuzz container builds; CR50 builds

Change-Id: If23c036c41a900bbcedd4b0bfd9edb1e89c17a0f
Reviewed-on: https://chromium-review.googlesource.com/822601
Commit-Ready: Nagendra Modadugu <ngm@google.com>
Tested-by: Nagendra Modadugu <ngm@google.com>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
diff --git a/Startup.c b/Startup.c
index 54df25b..053735c 100644
--- a/Startup.c
+++ b/Startup.c
@@ -163,8 +163,10 @@
    // The H-CRTM state no longer matters
    g_DrtmPreStartup = FALSE;
 
+#ifdef EMBEDDED_MODE
    if (startup == SU_RESET)
        _plat__ResetCallback();
+#endif
 
    return TPM_RC_SUCCESS;
 }