google-usb-network: Fix quotes

The name in d.getVar() should have been quoted.

Change-Id: I95468473268e24fcd97a681ac7baff9de2212278
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-google/recipes-google/networking/google-usb-network_git.bb b/meta-google/recipes-google/networking/google-usb-network_git.bb
index 95c2844..bf77187 100644
--- a/meta-google/recipes-google/networking/google-usb-network_git.bb
+++ b/meta-google/recipes-google/networking/google-usb-network_git.bb
@@ -26,7 +26,7 @@
 SRC_URI += "file://usb_network.sh"
 
 SYSTEMD_PACKAGES = "${PN}"
-SYSTEMD_SERVICE:${PN} = "${@"usb_network.service" if d.getVar(BMC_USB_ECM_PRODUCT_ID) else ""}"
+SYSTEMD_SERVICE:${PN} = "${@'usb_network.service' if d.getVar('BMC_USB_ECM_PRODUCT_ID') else ''}"
 
 do_compile:append() {
   if [ -n "${BMC_USB_ECM_PRODUCT_ID}" ]; then