drivers/srf02: adapted ultrasonic ranger driver to general i2c interface

This PR is based on  #1859. It changes the i2c commands in the sensor-driver to the general interface definition. It also adds a small test.
why not use `i2c_write_reg()` here? 

Suppose the function is changed to `srf02_read(srf02_t *dev)`
you can shorten this to `i2c_write_reg(dev->i2c, dev->addr, SRF02_COMMAND_REG, mode);`