snippet: Updated all snippet tags

Ensure all src C++ headers which have corresponding C++ examples have
doxygen tags which point to those examples.  Some were missing, some
were invalid, some needed to be updated to match the new example names.

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/nmea_gps/nmea_gps.hpp

@@ -61,7 +61,7 @@ namespace upm {
    * An example using the UART.
    * @snippet nmea_gps.cxx Interesting
    * An example using I2C.
-   * @snippet nmea_gps_i2c.cxx Interesting
+   * @snippet nmea_gps-i2c.cxx Interesting
    */
 
   class NMEAGPS {