add lzop decompression support

Add lzop decompression support to the existing lzo bitstream handling
(think gzip versus zlib), and support it for uImage decompression if
CONFIG_LZO is enabled.

Lzop doesn't compress as good as gzip (~10% worse), but decompression
is very fast (~0.7s faster here on a slow ppc). The lzop decompression
code is based on Albin Tonnerre's recent ARM Linux lzo support patch.

Cc: albin.tonnerre@free-electrons.com
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>