seccomp: support 32-bit arm on arm64, and 32-bit ppc on ppc64
seccomp: support 32-bit arm on arm64, and 32-bit ppc on ppc64

Generally we enforce that a [arch] seccomp section can only be used on [arch].
However, on amd64 we allow [i386] sections for i386 containers, and there we
also take [all] sections and apply them for both 32- and 64-bit.

Do that also for ppc64 and arm64.  This allows seccomp-protected armhf
containers to run on arm64.

Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>
Acked-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

aeris/lxc,LynxChaus/lxc,LynxChaus/lxc,tych0/lxc,armcc/lxc,ksperis/lxc,thmo/lxc,aeris/lxc,QingweiPeterLan/cs188-lxc,bostjan/lxc,aeris/lxc,GreatFruitOmsk/lxc,ysbnim/lxc,thmo/lxc,akshaykarle/lxc,caglar10ur/lxc,akshaykarle/lxc,cjwatson/lxc,caglar10ur/lxc,tych0/lxc,Distrotech/lxc,cjwatson/lxc,Distrotech/lxc,ss1h2a3tw/lxc,hfuCN/lxc,LynxChaus/lxc,hallyn/lxc,ksperis/lxc,akshaykarle/lxc,hfuCN/lxc,ysbnim/lxc,armcc/lxc,terceiro/lxc,hallyn/lxc,federicobriata/lxc,ysbnim/lxc,bostjan/lxc,caglar10ur/lxc,tych0/lxc,cjwatson/lxc,GreatFruitOmsk/lxc,hfuCN/lxc,bostjan/lxc,thmo/lxc,ss1h2a3tw/lxc,armcc/lxc,ksperis/lxc,QingweiPeterLan/cs188-lxc,GreatFruitOmsk/lxc,QingweiPeterLan/cs188-lxc,hallyn/lxc,federicobriata/lxc,federicobriata/lxc,Distrotech/lxc,terceiro/lxc,ss1h2a3tw/lxc,terceiro/lxc