drm/amdgpu: correct ih_chicken programming for vega10/vega20 ih blocks

IH_CHICKEN.MC_SPACE_FBPA_ENABLE field is only
valid when IH_RB_CNTL.MC_SPACE is programed to 0x3,
frame buffer physical address. For both bus address
and gpu virtual address, don't program MC_SPACE_FBPA_ENABLE
field

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Dennis Li <Dennis.Li@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>