drm/amd/display: Remove unnecessary NULL check

[Why]
new_crtc_state is already dereferenced earlier in the function

[How]
Remove the check
Signed-off-by: NEryk Brol <eryk.brol@amd.com>
Acked-by: NBindu Ramamurthy <bindu.r@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -9367,7 +9367,7 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 		if (ret)
 			goto fail;
 
-		if (dm_old_crtc_state->dsc_force_changed && new_crtc_state)
+		if (dm_old_crtc_state->dsc_force_changed)
 			new_crtc_state->mode_changed = true;
 	}