Quick fix for the floating point printer

Forgot to make it C-friendly by encapsulating the 'extern "C"' in an '#ifdef
__cplusplus' block.

Change-Id: I62988f4dea725f119027224d7d7beac1556c2621

springbok/include/springbok.h

diff --git a/springbok/include/springbok.h b/springbok/include/springbok.h
index a0a9d06..385d5b2 100644
--- a/springbok/include/springbok.h
+++ b/springbok/include/springbok.h
@@ -32,6 +32,12 @@
 #define LOG_NOISY(msg, args...) \
   SIMLOG(noisy, LOG_FMT msg, LOG_ARGS(NOISY_TAG), ##args)
 
-extern "C" int float_to_str(const int len, char *buffer, const float value);
+#ifdef __cplusplus
+extern "C" {
+#endif
+int float_to_str(const int len, char *buffer, const float value);
+#ifdef __cplusplus
+}
+#endif
 
 #endif