Revert "drm/amd/display: Add null check for 'afb' in amdgpu_dm_update_cursor"

[WHY]
This commit introduced a regression with kms_plane_cursor IGT
tests, causing AMD Asics to fail these tests.

This reverts commit ce66ffd9.
Reviewed-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Tested-by: George Zhang <George.zhang@amd.com>
Signed-off-by: Ivan Lipski <ivlipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -8637,22 +8637,14 @@ static void amdgpu_dm_update_cursor(struct drm_plane *plane,
 {
 	struct amdgpu_device *adev = drm_to_adev(plane->dev);
 	struct amdgpu_framebuffer *afb = to_amdgpu_framebuffer(plane->state->fb);
-	struct drm_crtc *crtc;
-	struct dm_crtc_state *crtc_state;
-	struct amdgpu_crtc *amdgpu_crtc;
-	u64 address;
+	struct drm_crtc *crtc = afb ? plane->state->crtc : old_plane_state->crtc;
+	struct dm_crtc_state *crtc_state = crtc ? to_dm_crtc_state(crtc->state) : NULL;
+	struct amdgpu_crtc *amdgpu_crtc = to_amdgpu_crtc(crtc);
+	uint64_t address = afb ? afb->address : 0;
 	struct dc_cursor_position position = {0};
 	struct dc_cursor_attributes attributes;
 	int ret;
 
-	if (!afb)
-		return;
-
-	crtc = plane->state->crtc ? plane->state->crtc : old_plane_state->crtc;
-	crtc_state = crtc ? to_dm_crtc_state(crtc->state) : NULL;
-	amdgpu_crtc = to_amdgpu_crtc(crtc);
-	address = afb->address;
-
 	if (!plane->state->fb && !old_plane_state->fb)
 		return;