[U-Boot] efi_loader: Fix partition offsets

[Alexander Graf]

> Commit 884bcf6f65 (efi_loader: use proper device-paths for partitions) tried
> to introduce the el torito scheme to all partition table types: Spawn
> individual disk objects for each partition on a disk.
> 
> Unfortunately, that code ended up creating partitions with offset=0 which meant
> that anyone accessing these objects gets data from the raw block device instead
> of the partition.
> 
> Furthermore, all the el torito logic to spawn devices for partitions was
> duplicated. So let's merge the two code paths and give partition disk objects
> good offsets to work from, so that payloads can actually make use of them.
> 
> Fixes: 884bcf6f65 (efi_loader: use proper device-paths for partitions)
> Reported-by: Yousaf Kaukab <yousaf.kaukab at suse.com>
> Signed-off-by: Alexander Graf <agraf at suse.de>

Thanks, applied to efi-next

Alex