UBUNTU: [Tests] gcc-multilib does not exist on ppc64el redux

Actually debian/control/tests can only have positive architectures
limits.  Switch this dependancy to a positive list.

BugLink: http://bugs.launchpad.net/bugs/1515541Signed-off-by: Andy Whitcroft <apw@canonical.com>

debian/tests/control

@@ -3,5 +3,5 @@ Depends: @builddeps@, fakeroot
 Restrictions: allow-stderr
 
 Tests: ubuntu-regression-suite
-Depends: build-essential, gcc-multilib [!ppc64el], gdb, git, bzr
+Depends: build-essential, gcc-multilib [amd64 arm64 armhf i386 powerpc], gdb, git, bzr
 Restrictions: allow-stderr, isolation-machine, breaks-testbed