NFS: Fix a regression in nfs_file_llseek()

NFS: Fix a regression in nfs_file_llseek()

commit 6c52961743f38747401b47127b82159ab6d8a7a4 upstream.

After commit 06222e491e663dac939f04b125c9dc52126a75c4 (fs: handle
SEEK_HOLE/SEEK_DATA properly in all fs's that define their own llseek)
the behaviour of llseek() was changed so that it always revalidates
the file size. The bug appears to be due to a logic error in the
afore-mentioned commit, which always evaluates to 'true'.

Reported-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>