owhw: add missing function board_exec_dbg_cmd

the board_exec_dbg_cmd function was not defined, causing a hard
fault on user input

Change-Id: I3ecc1f7bdb2484f5a67c36163d33ebc065e4e709
diff --git a/firmware/libboard/owhw/source/owhw.c b/firmware/libboard/owhw/source/owhw.c
index 91c1294..be62660 100644
--- a/firmware/libboard/owhw/source/owhw.c
+++ b/firmware/libboard/owhw/source/owhw.c
@@ -24,6 +24,24 @@
 
 static const Pin pins_cardsim[] = PINS_CARDSIM;
 
+void board_exec_dbg_cmd(int ch)
+{
+	switch (ch) {
+	case '?':
+		printf("\t?\thelp\n\r");
+		printf("\tR\treset SAM3\n\r");
+		break;
+	case 'R':
+		printf("Asking NVIC to reset us\n\r");
+		USBD_Disconnect();
+		NVIC_SystemReset();
+		break;
+	default:
+		printf("Unknown command '%c'\n\r", ch);
+		break;
+	}
+}
+
 void cardsim_set_simpres(uint8_t slot, int present)
 {
 	if (slot > 1)