jffs2: add compr=lzo and compr=zlib options

..to allow forcing of either compression scheme.  This will override
compiled-in defaults.  jffs2_compress is reworked a bit, as the lzo/zlib
override shares lots of code w/ the PRIORITY mode.

v2: update show_options accordingly.

Signed-off-by: Andres Salomon <[email protected]>
Signed-off-by: Artem Bityutskiy <[email protected]>
3 files changed