dfu: Only perform DFU board_usb_init() for TRATS

USB initialization shouldn't happen for all the boards.

Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>

common/cmd_dfu.c

diff --git a/common/cmd_dfu.c b/common/cmd_dfu.c
index 01d6b3a..327c738 100644
--- a/common/cmd_dfu.c
+++ b/common/cmd_dfu.c
@@ -55,7 +55,10 @@
 		goto done;
 	}
 
+#ifdef CONFIG_TRATS
 	board_usb_init();
+#endif
+
 	g_dnl_register(s);
 	while (1) {
 		if (ctrlc())