MIPS: Octeon: remove orphan octeon_hal_setup_reserved32() declaration

All uses of octeon_hal_setup_reserved32() were removed by
commit 1ef28870 ("MIPS: Octeon: Remove vestiges of
CONFIG_CAVIUM_RESERVE32_USE_WIRED_TLB"), so remove the
orphan declaration, too.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>