servod: Fix up _init_ftdi_gpiouart.

Forgot to pass in vendor, product and serial to _init_ftdi_gpio inside
_init_ftdi_gpiouart.  This should have been failing on all the devices
using ftdi_gpiouart (miniservo, toad, reston, fruitpie, plankton).

BUG=None
TEST=None

Change-Id: Ia95dcc8599d2edaa5de3fa94785a97deb46218cf
Reviewed-on: https://chromium-review.googlesource.com/365402
Commit-Ready: Kevin Cheng <kevcheng@chromium.org>
Tested-by: Kevin Cheng <kevcheng@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
diff --git a/servo/servo_server.py b/servo/servo_server.py
index a78fc01..46ac716 100755
--- a/servo/servo_server.py
+++ b/servo/servo_server.py
@@ -404,7 +404,7 @@
     Raises:
       ServodError: If init fails
     """
-    fgpio = self._init_ftdi_gpio(interface)
+    fgpio = self._init_ftdi_gpio(vendor, product, serialname, interface)
     fuart = ftdiuart.Fuart(vendor, product, interface, serialname, fgpio._fc)
     try:
       fuart.run()