Update printf.rst

Clarifies the need for ti/real.h library by including it in the code snippet

docs/static/printf.rst

@@ -19,10 +19,12 @@ To disable all other printf functions and use this `sprintf` implementation, add
 
     HAS_PRINTF = NO
 
-If you just need to convert a float to a string, which the OS sprintf does not support, you can utilize the following `float2str` function by including `ti/real.h` instead.
+If you just need to convert a float to a string, which the OS sprintf does not support, you can utilize the following `float2str` function instead.
 
 .. code-block:: c
 
+    #include <ti/real.h>
+
     void float2str(float value, char *str)
     {
         real_t tmp_real = os_FloatToReal(value);