usb.c: Fix error introducing Tx underflows

In Change-Id I7d4d4ab39cb3e7e6a7eb8e738a367122eb3fbee2 I inroduced
a bug that would cause e1_usb_xfer_out() to return four bytes too
little, which in turn causes E1 Tx underflows to happen in the device
firmware.

Change-Id: I71675d4de781421286f0d1febedfdb1f7b523c38

1 files changed, 1 insertions, 1 deletions

diff --git a/src/usb.c b/src/usb.c
index e8cd212..7a5dce2 100644
--- a/src/usb.c
+++ b/src/usb.c
@@ -135,7 +135,7 @@ e1_usb_xfer_out(struct e1_usb_flow *flow, uint8_t *buf, int size)
 
 	memset(buf, 0xff, 4);
 
-	return e1_line_mux_out(line, buf+4, fts);
+	return e1_line_mux_out(line, buf+4, fts) + 4;
 }
 
 static int