Remove armeb/arm from KNOWN_ARCHS.
Remove armeb from arm universe targets.
Remove armeb from arch.7
Remove all the details about armeb from arch(7), except for its
release start and end, like alpha, ia64 and pc98.
Remove kernel support for armeb
Remove all the big-endian arm architectures (ixp425 and ixp435)
support in the kernel and associated drivers.
Remove special cases for armeb in the build.