xfs: simplify xfs_rmap_lookup_le call sites

xfs: simplify xfs_rmap_lookup_le call sites

Source kernel commit: 5b7ca8b313621907d80460bfcc1fa876d2a38488

Most callers of xfs_rmap_lookup_le will retrieve the btree record
immediately if the lookup succeeds.  The overlapped version of this
function (xfs_rmap_lookup_le_range) will return the record if the lookup
succeeds, so make the regular version do it too.  Get rid of the useless
len argument, since it's not part of the lookup key.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>