google/coral: Fetch SKU ID from EC

BUG=b:64468585
BRANCH=none
TEST=with the other sku-id related patches applied, coreboot obtains the
right SKU ID from EC

Change-Id: I96a0e030bbc5f1c98165e70353340c413f8dc352
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/20947
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/mainboard/google/reef/variants/coral/mainboard.c

@@ -14,11 +14,13 @@
  */
 
 #include <stdint.h>
+#include <ec/google/chromeec/ec.h>
 #include "baseboard/variants.h"
 
 uint8_t variant_board_sku(void)
 {
-	return 0;
+	// we know that the values are in 0..255
+	return google_chromeec_get_sku_id();
 }
 
 void variant_nhlt_oem_overrides(const char **oem_id,