xfs_bmap: don't reject -e

xfs_bmap: don't reject -e

The xfs_io bmap command has an -e switch that prints delalloc extents
without fsync'ing the file first.  The xfs_bmap manpage says it'll pass
-e through, but it doesn't.  Fix the script and fix the weird manpage
discrepancy where it doesn't list -e in the available options but
discusses it anyway.

Fixes: 7536ce44f6 ("xfs_io: bmap should support querying CoW fork, shared blocks")
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>