smbios: Expose in efi_loader as table

We can pass SMBIOS easily as EFI configuration table to an EFI payload. This
patch adds enablement for that case.

While at it, we also enable SMBIOS generation for ARM systems, since they support
EFI_LOADER.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>