docs: added new sensor images

Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

src/mpu9150/mpu60x0.h

@@ -55,6 +55,7 @@ namespace upm {
    * should allow an end user to implement whatever features are
    * required.
    *
+   * @image html mpu60x0.jpg
    * @snippet mpu60x0.cxx Interesting
    */
   class MPU60X0 {

src/mpu9150/mpu9250.h

@@ -46,6 +46,7 @@ namespace upm {
    *
    * This module defines the MPU9250 interface for libmpu9150
    *
+   * @image html mpu9250.jpg
    * @snippet mpu9250.cxx Interesting
    */