chromeos / broadwell / jecht: Make save_chromeos_gpios() jecht-specific

This callback was only required for a single mainboard, and it can
easily be moved to mainboard-specific code. This patch removes it from
the global namespace and isolates it to the Jecht board. (This makes
it easier to separate vboot and chromeos code in a later patch.)

Change-Id: I9cf67a75a052d1c86eda0393b6a9fbbe255fedf8
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/18981
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/mainboard/google/jecht/chromeos.c

@@ -22,6 +22,7 @@
 #include <ec/google/chromeec/ec.h>
 #include <soc/gpio.h>
 #include <soc/sata.h>
+#include "onboard.h"
 
 #define GPIO_SPI_WP	58
 #define GPIO_REC_MODE	12