please ignore pocl autopkgtest failure on ppc64el

[Andreas Beckmann <anbe@debian.org>]

Hi,

please temporarily ignore the autopkgtest failure of pocl on ppc64el. 
pocl just gained a first superficial autopkgtest, but it is not built on 
ppc64el and therefore not installable ... causing a "regression"
I'll add the skip-not-installable restriction in the next upload.

Thanks

Andreas