mainboard/google/samus: Fix usage of GNU field designator ext

Following the reasoning in,
 8089f17 mainboard/lenovo/x230 Fix usage of GNU field designator extension

In C99 we defined a syntax for this. GCC's old syntax was deprecated.

Change-Id: Id3b16872f62660393d938d6f95977a4e3842d0d1
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/7690
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/mainboard/google/samus/romstage.c

@@ -146,7 +146,7 @@ void mainboard_romstage_entry(unsigned long bist)
 			{ 0x0040, 1, USB_OC_PIN_SKIP,	/* P7: BT */
 			  USB_PORT_INTERNAL },
 		},
-		usb3_ports: {
+		.usb3_ports = {
 			/* Enable, OCn# */
 			{ 1, 0               }, /* P1: HOST PORT */
 			{ 1, 1               }, /* P2: HOST PORT  */