busybox

ash: remove no-longer-used variable

As of 035486c75 (ash: significant overhaul of redirect saving logic,
2017-07-31), the sv_pos variable is no longer used (just assigned to,
with no further effect).

Let's just remove it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>