Return the actual out of bounds size per page instead of the ioctl
return status. JFFS2 will happily operate with an OOB size of 0 and
instead put cleanmarkers in the normal page space of the flash.
The maximum size of JFFS2 is 4GB minus the block size of the flash.
Enforce this limitation when setting up a filesystem on a flashdev
region that is larger than the maximum.
This also resolves some off-nominal memory leaks.
This adds generic JFFS2 interworking code that allows JFFS2 to be used
on top of any flashdev backend. It currently only supports NOR flashdev
backends.
