MIPS: Octeon: Remove SYS_SUPPORTS_HIGHMEM.

Only 64-bit kernels are supported, no need for SYS_SUPPORTS_HIGHMEM

Signed-off-by: Chandrakala Chavva <cchavva@caviumnetworks.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2988/


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