mraa.c: Find i2c bus by pci id

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

include/mraa_internal.h

@@ -149,6 +149,16 @@ int mraa_find_i2c_bus(const char* devname, int startfrom);
  */
 mraa_result_t mraa_atoi(char* intStr, int* value);
 
+/**
+ * helper function to find an i2c bus based on pci data
+ *
+ * @param pci_device
+ * @param pci_id on pci_device
+ * @param i2c adapter name & number
+ * @return the matching i2c-dev bus id or -1
+ */
+int mraa_find_i2c_bus_pci(const char* pci_device, const char *pci_id, const char* adapter_name);
+
 #if defined(IMRAA)
 /**
  * read Imraa subplatform lock file, caller is responsible to free return