drm/amdgpu: fix the gb_addr_config_fields init value mismatch
For gfx_v9_4_3 specifically, before regGB_ADDR_CONFIG is overwritten
in gfx hw_init it is read out to popluate the gb_addr_config_fields
in the sw_init stage, which causes mismatch.
Fix it by using the golden value in sw_init as well.
v2: This is a driver-set golden reg and keep as it is (Lijo)