xfsprogs: remove setfl from xfs_io

xfsprogs: remove setfl from xfs_io

Doesn't seem to have worked for ages, and is (therefore)
apparently not ever used:

xfs_io> setfl
xfs_io> help setfl
setfl [-adx] -- set/clear append/direct flags on the open file
xfs_io> setfl -a
bad argument count 1 to setfl, expected 0 arguments
xfs_io> setfl -d
bad argument count 1 to setfl, expected 0 arguments
xfs_io> setfl
xfs_io>

At best, it seems intended to toggle the flag state, but
gives no feedback about current state.  -x is in help but
not implemented, etc.

Just remove it.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Mark Tinguely <tinguely@sgi.com>