Fix HardwareSerial peek() and read() functions for TivaC
Fix HardwareSerial peek() and read() functions for TivaC

- peek() would loop forever if the RX buffer was empty.
- read() would increase the buffer read pointer even if no byte was read because the buffer was empty.

martianmartin/Energia,dvdvideo1234/Energia,bobintornado/Energia,NoPinky/Energia,vigneshmanix/Energia,vigneshmanix/Energia,dvdvideo1234/Energia,bobintornado/Energia,qtonthat/Energia,dvdvideo1234/Energia,vigneshmanix/Energia,sanyaade-iot/Energia,martianmartin/Energia,bobintornado/Energia,dvdvideo1234/Energia,danielohh/Energia,martianmartin/Energia,radiolok/Energia,battosai30/Energia,danielohh/Energia,sanyaade-iot/Energia,brianonn/Energia,cevatbostancioglu/Energia,dvdvideo1234/Energia,qtonthat/Energia,battosai30/Energia,battosai30/Energia,brianonn/Energia,brianonn/Energia,dvdvideo1234/Energia,vigneshmanix/Energia,NoPinky/Energia,DavidUser/Energia,bobintornado/Energia,brianonn/Energia,radiolok/Energia,battosai30/Energia,sanyaade-iot/Energia,DavidUser/Energia,NoPinky/Energia,radiolok/Energia,qtonthat/Energia,martianmartin/Energia,cevatbostancioglu/Energia,danielohh/Energia,bobintornado/Energia,croberts15/Energia,sanyaade-iot/Energia,brianonn/Energia,croberts15/Energia,croberts15/Energia,DavidUser/Energia,DavidUser/Energia,DavidUser/Energia,radiolok/Energia,croberts15/Energia,martianmartin/Energia,sanyaade-iot/Energia,danielohh/Energia,radiolok/Energia,DavidUser/Energia,danielohh/Energia,radiolok/Energia,cevatbostancioglu/Energia,croberts15/Energia,bobintornado/Energia,sanyaade-iot/Energia,brianonn/Energia,NoPinky/Energia,battosai30/Energia,martianmartin/Energia,bobintornado/Energia,cevatbostancioglu/Energia,battosai30/Energia,NoPinky/Energia,danielohh/Energia,dvdvideo1234/Energia,martianmartin/Energia,qtonthat/Energia,cevatbostancioglu/Energia,croberts15/Energia,sanyaade-iot/Energia,danielohh/Energia,brianonn/Energia,battosai30/Energia,croberts15/Energia,NoPinky/Energia,qtonthat/Energia,qtonthat/Energia,cevatbostancioglu/Energia,cevatbostancioglu/Energia,radiolok/Energia,vigneshmanix/Energia,DavidUser/Energia,qtonthat/Energia,NoPinky/Energia,vigneshmanix/Energia,vigneshmanix/Energia