drm/radeon/radeon_ttm: Place declaration of 'rdev' in same clause as its use

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/radeon/radeon_ttm.c: In function ‘radeon_ttm_tt_create’:
 drivers/gpu/drm/radeon/radeon_ttm.c:611:24: warning: variable ‘rdev’ set but not used [-Wunused-but-set-variable]

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jerome Glisse <glisse@freedesktop.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_ttm.c

@@ -608,20 +608,18 @@ static void radeon_ttm_backend_destroy(struct ttm_bo_device *bdev, struct ttm_tt
 static struct ttm_tt *radeon_ttm_tt_create(struct ttm_buffer_object *bo,
 					   uint32_t page_flags)
 {
-	struct radeon_device *rdev;
 	struct radeon_ttm_tt *gtt;
 	enum ttm_caching caching;
 	struct radeon_bo *rbo;
-
-	rbo = container_of(bo, struct radeon_bo, tbo);
-
-	rdev = radeon_get_rdev(bo->bdev);
 #if IS_ENABLED(CONFIG_AGP)
+	struct radeon_device *rdev = radeon_get_rdev(bo->bdev);
+
 	if (rdev->flags & RADEON_IS_AGP) {
 		return ttm_agp_tt_create(bo, rdev->ddev->agp->bridge,
 					 page_flags);
 	}
 #endif
+	rbo = container_of(bo, struct radeon_bo, tbo);
 
 	gtt = kzalloc(sizeof(struct radeon_ttm_tt), GFP_KERNEL);
 	if (gtt == NULL) {