mips: Remove CONFIG_VT82C686 from non-Fulong configs

mips: Remove CONFIG_VT82C686 from non-Fulong configs

Fix the regression introduced with commit
47934d0aadc075b05ce2d9e8a44fa6a46edd1afa [hw: move ISA bridges and
devices to hw/isa/, configure with default-configs/], by removing
CONFIG_VT82C686 from configurations that previously did not enable it.
That southbridge is only available on Fulong platforms (CONFIG_FULONG)
that are exclusively little-endian, 64-bit MIPS.  Previously vt82c686.o
was pulled explicitly with obj-$(CONFIG_FULONG).

Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>