[pnfs] inode_lock() needed for pnfs client

[William A.(Andy) Adamson]

i've been running with a patch which exports the inode_lock() symbol from 
fs/inode.c.

the inode_lock() is used by the pnfs client recall_layout_thread() in 
fs/nfs/delegation.c

i'm suprised nobody has checked this in. if there are no objections, i'll 
check this into the CVS tree, as it is part of the pNFS layer, and which will 
be changed at a later date.

-->Andy