NFSv4: Express delegation limit in units of pages

Since we're tracking modifications to the page cache on a per-page
basis, it makes sense to express the limit to how much we may cache
in units of pages.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --cc fs/nfs/delegation.c
Simple merge

diff --cc fs/nfs/delegation.h
Simple merge

diff --cc fs/nfs/nfs4xdr.c
Simple merge

diff --cc include/linux/nfs_xdr.h
Simple merge