drm/amd: Drop special case for yellow carp without discovery

`amdgpu_gmc_get_vbios_allocations` has a special case for how to
bring up yellow carp when amdgpu discovery is turned off. As this ASIC
ships with discovery turned on, it's generally dead code and worse it
causes `adev->mman.keep_stolen_vga_memory` to not be initialized for
yellow carp.

Remove it.
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -725,12 +725,6 @@ void amdgpu_gmc_get_vbios_allocations(struct amdgpu_device *adev)
 	case CHIP_RENOIR:
 		adev->mman.keep_stolen_vga_memory = true;
 		break;
-	case CHIP_YELLOW_CARP:
-		if (amdgpu_discovery == 0) {
-			adev->mman.stolen_reserved_offset = 0x1ffb0000;
-			adev->mman.stolen_reserved_size = 64 * PAGE_SIZE;
-		}
-		break;
 	default:
 		adev->mman.keep_stolen_vga_memory = false;
 		break;