nfs: fix nfs_size_to_loff_t

nfs: fix nfs_size_to_loff_t

[ Upstream commit 50ab8ec74a153eb30db26529088bc57dd700b24c ]

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We support OFFSET_MAX just fine, so don't round down below it.  Also
switch to using min_t to make the helper more readable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 433c92379d9c ("NFS: Clean up nfs_size_to_loff_t()")
Cc: stable@vger.kernel.org # 2.6.23+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>