minor: fix linker warning

linker warning:
obj/simtrace/dfu_sniffer.o: In function `usb_send_data':
/media/data/work/simtrace2/simtrace2/firmware/libcommon/source/sniffer.c:338: warning: undefined reference to `putchar'

Change-Id: I934f3fcb474d4046e921511a024c3a0b8533c782

firmware/libcommon/source/sniffer.c

@@ -335,7 +335,7 @@ static void usb_send_data(enum simtrace_msg_type_sniff type, const uint8_t* data
 				printf(", ");
 			}
 		}
-		printf(")");
+		putchar(')');
 	}
 	printf(": ");
 	uint16_t i;