Fixed FW-258. The UART peripheral of the CC2538 has a shadow register that needs to be emptied by a timeout interrupt, otherwise the last byte does not get processed until a new byte arrives. This affects the communication with OpenVisualizer since it relies on communicating full HDLC frames.
Removed the initialization delay of the UART peripheral since it is no longer required.
Merge pull request #98 from OpenMote/develop

FW-258. Fix.