lightnvm: use system block for mm initialization

Use system block information to register the appropriate media manager.
This enables the LightNVM subsystem to instantiate a media manager
selected by the user, instead of relying on automatic detection by each
media manager loaded in the kernel.

A device must now be initialized before it can proceed to initialize its
media manager. Upon initialization, the configured media manager is
automatically initialized as well.

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

include/linux/lightnvm.h

@@ -301,6 +301,9 @@ struct nvm_dev {
 	struct nvmm_type *mt;
 	void *mp;
 
+	/* System blocks */
+	struct nvm_sb_info sb;
+
 	/* Device information */
 	int nr_chnls;
 	int nr_planes;