firmware/sniffer: Enable interrupts for overrun/parity/frame errors

We so far didn't have interrupts enabled for those, and just caught
them "by accident" if a byte was received or if a timeout happened.

Let's explicitly enable those interrupts so we also catch those
conditions by themselves.

Change-Id: Ia27f537706b9a6252dd18175545c6f27a7d17d0e

firmware/libcommon/source/sniffer.c

@@ -918,7 +918,7 @@ void Sniffer_usart0_irq(void)
  * Initialization routine
  *-----------------------------------------------------------------------------*/
 
-#define SNIFFER_IER (US_IER_RXRDY | US_IER_TIMEOUT)
+#define SNIFFER_IER (US_IER_RXRDY | US_IER_TIMEOUT | US_IER_OVRE | US_IER_FRAME | US_IER_PARE)
 
 /* Called during USB enumeration after device is enumerated by host */
 void Sniffer_configure(void)