fastboot: add vendor_boot to list of images

The vendor_boot partition has been created, so add it to the list of
images which may be flashed.

Bug: 137297791
Change-Id: I27eaa16656a83dbcb8289680844bf58dd1fccf24
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 8923f40..5bd37e1 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -160,6 +160,10 @@
                                                       "vbmeta_system",
                                                                   true,  ImageType::BootCritical },
     { "vendor",   "vendor.img",       "vendor.sig",   "vendor",   true,  ImageType::Normal },
+    { "vendor_boot",
+                  "vendor_boot.img",  "vendor_boot.sig",
+                                                      "vendor_boot",
+                                                                  true,  ImageType::BootCritical },
     { nullptr,    "vendor_other.img", "vendor.sig",   "vendor",   true,  ImageType::Normal },
         // clang-format on
 };