NFSv4.1: pnfs: filelayout: add driver's LAYOUTGET and GETDEVICEINFO infrastructure

NFSv4.1: pnfs: filelayout: add driver's LAYOUTGET and GETDEVICEINFO infrastructure

Implement the driver's io_ops->alloc_lseg and free_lseg functions,
which integrate into the deviceid cache and calls out to
nfs4_proc_getdeviceinfo when necessary.

Signed-off-by: Andy Adamson <[email protected]>
Signed-off-by: Dean Hildebrand <[email protected]>
Signed-off-by: Marc Eshel <[email protected]>
Signed-off-by: Mike Sager <[email protected]>
Signed-off-by: Oleg Drokin <[email protected]>
Signed-off-by: Ricardo Labiaga <[email protected]>
Signed-off-by: Tao Guo <[email protected]>
Signed-off-by: Boaz Harrosh <[email protected]>
Signed-off-by: Fred Isaman <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>