MIPS: Loongson2ef: remove orphan sbx00_acpi_init() declaration

All uses of sbx00_acpi_init() in the "pci.c" file were removed by
commit 5831fdb0 ("MIPS: Loongson2ef: clean up loongson64
related code"), so remove the orphan declaration, too.

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