api: Added mraa_has_sub_platform() function

Signed-off-by: Henry Bruce <henry.bruce@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/mraa/common.h

@@ -188,6 +188,14 @@ char* mraa_get_pin_name(int pin);
  */
 int mraa_get_default_2c_bus();
 
+/**
+ * Detect presence of sub platform.
+ *
+ * @return mraa_boolean_t 1 if sub platform is present and initialized, 0 otherwise
+ */
+mraa_boolean_t mraa_has_sub_platform();
+
+
 /**
  * Select main platform for platform info calls.
  *