[coreboot] vboot/futility: Two Clang 5 warnings: address-of-packed-member and enum-conversion

[Stefan Reinauer]

Dear Paul,

* Paul Menzel <paulepanter at users.sourceforge.net> [171007 11:05]:
> Dear coreboot folks,
> 
> 
> Clang 5.0 shows the warnings below. I don’t know if Clang 4.0 also
> warns about these.
> 
> ```
>     CC            firmware/lib/vboot_api_kernel.o
> firmware/lib/vboot_api_kernel.c:334:26: error: taking address of packed member 'kernel_version_tpm' of class or structure
>       'VbSharedDataHeader' may result in an unaligned pointer value [-Werror,-Waddress-of-packed-member]
>         if (RollbackKernelRead(&shared->kernel_version_tpm)) {
>                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~
> firmware/lib/vboot_api_kernel.c:512:16: error: implicit conversion from enumeration type 'enum vb2_nv_param' to different enumeration type
>       'VbNvParam' (aka 'enum VbNvParam') [-Werror,-Wenum-conversion]
>         VbNvGet(&vnc, VB2_NV_DEV_BOOT_FASTBOOT_FULL_CAP,
>         ~~~~~~~       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 2 errors generated.
> ```

Clang is not currently supported by coreboot. However, if you wish to
contribute a patch to fix above issues, it will probably get merged.

Stefan