Change kernel vboot header layout and add support for separate header verification.

src/platform/vboot_reference/tests/kernel_image_tests.c

Index: src/platform/vboot_reference/tests/kernel_image_tests.c
diff --git a/src/platform/vboot_reference/tests/kernel_image_tests.c b/src/platform/vboot_reference/tests/kernel_image_tests.c
index 15f75bd418a57c9b1a0e822d2d61a286ca4bdd80..4890de3a18bfee219e82e6294c1ca9f364d4c65b 100644
--- a/src/platform/vboot_reference/tests/kernel_image_tests.c
+++ b/src/platform/vboot_reference/tests/kernel_image_tests.c
@@ -40,14 +40,14 @@ void VerifyKernelImageTest(KernelImage* image,
 /* Tampered KernelImage Verification Tests. */
 void VerifyKernelImageTamperTest(KernelImage* image,
                                  RSAPublicKey* firmware_key) {
-  image->kernel_config[0] ^= 0xFF;
+  image->bootloader_offset ^= 0xFF;
   TEST_EQ(VerifyKernelImage(firmware_key, image, DEV_MODE_ENABLED),
-          VERIFY_KERNEL_CONFIG_SIGNATURE_FAILED,
+          VERIFY_KERNEL_PREAMBLE_SIGNATURE_FAILED,
           "KernelImage Config Tamper Verification (Dev Mode)");
   TEST_EQ(VerifyKernelImage(firmware_key, image, DEV_MODE_DISABLED),
-          VERIFY_KERNEL_CONFIG_SIGNATURE_FAILED,
+          VERIFY_KERNEL_PREAMBLE_SIGNATURE_FAILED,
           "KernelImage Config Tamper Verification (Trusted)");
-  image->kernel_config[0] ^= 0xFF;
+  image->bootloader_offset ^= 0xFF;
 
   image->kernel_data[0] = 'T';
   TEST_EQ(VerifyKernelImage(firmware_key, image, DEV_MODE_ENABLED),