test: spl: Add a test for the NOR load method

Add a test for the NOR load method. Since NOR is memory-mapped we can
substitute a buffer instead. The only major complication is testing LZMA
decompression.  It's too complex to implement LZMA compression in a test, and we
have no in-tree compressor, so we just include some pre-compressed data. This
data was generated through something like

    generate_data(plain, plain_size, "lzma")
    cat plain.dat | lzma | hexdump -C

and was cleaned up further in my editor.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>