Fixed UART driver

The original interrupt handler occasionally hang in case of noise on the line. 
Fixes were two:
1) Disable IDLE line interrupt, disable LIN break interrupt (neither of them should be used for asynchronous single buffer communication) in the port settings.
2) In interrupt handler routine, explicitly check for the error flags, only if no errors occur, check the received byte. Otherwise clear the USART_DR and log the error.

Error logging variables are added to monitor errors on the port.