buildroot

lpty: remove LPTY_VERSION_UPSTREAM

It is not used for anything.

Note that the SUBDIR is NOT the usual lpty-$(LPTY_VERSION_UPSTREAM);
it *does* have the rockspec version in its name.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>