drm/amdgpu/display: drop set but unused variable

Fixes this warning:
drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:9143:27: warning: variable 'abo' set but not used [-Wunused-but-set-variable]

Fixes: 047de3f1 ("drm/amdgpu: switch DM to atomic fence helpers v2")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220616203538.649041-1-alexander.deucher@amd.com

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

@@ -9139,7 +9139,6 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 			to_dm_crtc_state(drm_atomic_get_old_crtc_state(state, pcrtc));
 	int planes_count = 0, vpos, hpos;
 	unsigned long flags;
-	struct amdgpu_bo *abo;
 	uint32_t target_vblank, last_flip_vblank;
 	bool vrr_active = amdgpu_dm_vrr_active(acrtc_state);
 	bool pflip_present = false;
@@ -9211,7 +9210,6 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 			continue;
 		}
 
-		abo = gem_to_amdgpu_bo(fb->obj[0]);
 		fill_dc_plane_info_and_addr(
 			dm->adev, new_plane_state,
 			afb->tiling_flags,