Some hardware that is supported by U-Boot can not handle DMA above 32bits.
For these systems, we need to come up with a way to expose the disk interface
in a safe way.

This patch implements EFI specific bounce buffers. For non-EFI cases, this
apparently was no issue so far, since we can just define our environment
variables conveniently.
Signed-off-by: NAlexander Graf <agraf@suse.de>