vendorcode/google: Use C99 flexible arrays

Use C99 flexible arrays instead of older style of one-element or
zero-length arrays.
It allows the compiler to generate errors when the flexible array does
not occur at the end in the structure.

Change-Id: I81ae8acb0365af102e513b3d7cfa1a824636eb06
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76812
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/vendorcode/google/chromeos/vpd_calibration.c

@@ -39,7 +39,7 @@ struct calibration_blob {
  */
 struct calibration_entry {
 	uint32_t size;
-	struct calibration_blob entries[0];  /* A varialble size container. */
+	struct calibration_blob entries[];  /* A varialble size container. */
 };