MIPS: OCTEON: Enable little endian kernel.

Now it is supported, so let people select it.

[ralf@linux-mips.org: Folded in fix for bogus CONFIG_ kconfig symbol
prefix.  Issue reported by Valentin Rothberg <valentinrothberg@gmail.com>.]

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Leonid Rosenboim <lrosenboim@caviumnetworks.com>
Signed-off-by: Aleksey Makarov <aleksey.makarov@auriga.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9592/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>