lightnvm: fix missing grown bad block type

The get/set bad block interface defines good block, factory bad block,
grown bad block, device reserved block, and host reserved block.
Unfortunately the grown bad block was missing, leaving the offsets wrong
for device and host side reserved blocks.

This patch adds the missing type and corrects the offsets.

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