busybox: add patch to fix 'head -n -1'

Busybox 1.29.0 introduces a regression causing head to fail with negative
'-n' parameters, e.g. 'head -n -1'. Instead of showing all but the last one
line, no lines are printed whatsoever.

The issue was reported with
http://lists.busybox.net/pipermail/busybox/2018-August/086617.html

 . This
commit backports the revert applied upstream.

Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>