We don't use ARM_ARCH_6 in the tree, and haven't for a long long
time. Remove it from here. As far as I could tell, nothing in ports
use it (either ARM_ARCH or ARM_ARCH_6__ is used in all the
apatches). We do have a define for _ARM_ARCH_6, but it's mostly unused
(and will remain, since it isn't in this file).