repair: allocate and free inode records individually

repair: allocate and free inode records individually

Instead of allocating inode records in chunks and keeping a freelist of them
which never gets released to the system memory allocator use plain malloc
and free for them.  The freelist just means adding a global lock instead
of relying on malloc and free which could be implemented lockless, and the
freelist is almost completely worthless as we are done allocating new
inode records once we start freeing them in major quantities.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>