Pca9685 pwm should not subclass I2C (#661)

* Remove erroneous use of base class I2C with PCA9685PWM.

I2C base class is for I2C ports in MCUs, not for I2C-connected devices.

src/freertos_drivers/common/PCA9685PWM.hxx

@@ -33,16 +33,19 @@
 
 #include <fcntl.h>
 #include <unistd.h>
+#include "stropts.h"
+#include "i2c.h"
+#include "i2c-dev.h"
 
-#include "I2C.hxx"
 #include "PWM.hxx"
 
+
 #include "os/OS.hxx"
 
 class PCA9685PWMBit;
 
 /// Agragate of 16 PWM channels for a PCA9685PWM
-class PCA9685PWM : public I2C, public OSThread
+class PCA9685PWM : public OSThread
 {
 public:
     /// maximum number of PWM channels supported by the PCA9685
@@ -53,8 +56,7 @@ public:
 
     /// Constructor.
     PCA9685PWM()
-        : I2C(name)
-        , sem_(0)
+        : sem_(0)
         , i2c_(-1)
         , dirty_(0)
         , i2cAddress_(0)