cuttlefish: Add support for vendor boot header v4

No acutal change in behavior outside of gathering more info from the
boot header.
Vendor boot header v4 comes with ramdisk fragment changes and bootconfig
Boot header v4 has no changes.
Vendor ramdisk fragments aren't being handled in any special way, and
the vendor ramdisk can continue to be placed into memory as is.
Bootconfig support comes in a follow-on commit.

Test: boot cuttlefish using a boot image with v4 header
Bug: 173815685
Change-Id: If9213f51ea4cb75c8274d4a6986c3422d11a379b
2 files changed