i2c_use_client() contains a bogosity.  If i2c_inc_use_client() returns
success, i2c_use_client() returns an error.  If i2c_inc_use_client()
fails, i2c_use_client() might succeed.

Fix it so that (a) we get the correct sense between these two functions,
and (b) propagate the error code from i2c_inc_use_client(), rather than
making our own one up.