drm/amdgpu/gmc9: add vega12 support (v2)

Same as vega10.

v2: squash in golden regs fix from Feifei
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>

drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c

@@ -791,6 +791,7 @@ static int gmc_v9_0_mc_init(struct amdgpu_device *adev)
 	if (amdgpu_gart_size == -1) {
 		switch (adev->asic_type) {
 		case CHIP_VEGA10:  /* all engines support GPUVM */
+		case CHIP_VEGA12:  /* all engines support GPUVM */
 		default:
 			adev->gmc.gart_size = 512ULL << 20;
 			break;
@@ -849,6 +850,7 @@ static int gmc_v9_0_sw_init(void *handle)
 		}
 		break;
 	case CHIP_VEGA10:
+	case CHIP_VEGA12:
 		/*
 		 * To fulfill 4-level page support,
 		 * vm size is 256TB (48bit), maximum size of Vega10,
@@ -965,6 +967,8 @@ static void gmc_v9_0_init_golden_registers(struct amdgpu_device *adev)
 						golden_settings_athub_1_0_0,
 						ARRAY_SIZE(golden_settings_athub_1_0_0));
 		break;
+	case CHIP_VEGA12:
+		break;
 	case CHIP_RAVEN:
 		soc15_program_register_sequence(adev,
 						golden_settings_athub_1_0_0,