fs/ext2: add support for ext2 rev0 and rev1

Some bootloaders have a buggy ext2 support, and require ext2 rev1
instead of the traditional ext2 rev0 that genext2fs produces.

tune2fs accepts only one '-O list' at a time, so we need to construct
a list of -O options.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>