The specification was changed to reflect a multi-value bad block table.
Instead of bit-based bad block table, the bad block table now allows
eight bad block categories. Currently four are defined:

 * Factory bad blocks
 * Grown bad blocks
 * Device-side reserved blocks
 * Host-side reserved blocks

The factory and grown bad blocks are the regular bad blocks. The
reserved blocks are either for internal use or external use. In
particular, the device-side reserved blocks allows the host to
bootstrap from a limited number of flash blocks. Reducing the flash
blocks to scan upon super block initialization.

Support for both get bad block table and set bad block table is added.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

The implementation for Open-Channel SSDs is divided into media
management and targets. This patch implements a generic media manager
for open-channel SSDs. After a media manager has been initialized,
single or multiple targets can be instantiated with the media managed as
the backend.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>