drm/amdgpu: fix SI's GB_ADDR_CONFIG_GOLDEN values and wire up sid.h in GFX6

By wiring up sid.h in GFX6, we end up with a few duplicated defines such as
the golden registers. Let's clean this up.

[TAHITI,VERDE, HAINAN]_GB_ADDR_CONFIG_GOLDEN were defined both in sid.h
and under si_enums.h, with different values. Keep the values used under radeon
and move them under gfx_v6_0.c where they are used (as it is done under cik)

Signed-off-by: Alexandre Demers <alexandre.f.demers@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>