[U-Boot] [PATCHv2] Add support for LZ4 decompression algorithm

[Julius Werner]

Well then... a few hours and a significant reduction in sanity later,
I found that I'm shadowing the new 'ret' variable from changing the
API around because I forgot to remove the declaration part from the
'ret' that already existed in the else block. It would be nice if
U-Boot compiled with -Wshadow...

This made the (outer) return variable uninitialized in the compression
error case, which on my native x86_64 happened to produce a non-zero
value... but with an i686 cross-compiler I could reproduce the error
you saw. Fixed in the next version and moved the config to
sandbox_defconfig as you suggested.