drm/amd/powerplay: fix a reversed condition

BugLink: http://bugs.launchpad.net/bugs/1546572

This test was reversed so it would end up leading to a NULL dereference.

Fixes: 4630f0fa ('drm/amd/powerplay: add Carrizo smu support')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 2500a3c9)
Signed-off-by: Alberto Milone <alberto.milone@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/gpu/drm/amd/powerplay/smumgr/cz_smumgr.c

@@ -818,7 +818,7 @@ static int cz_smu_fini(struct pp_smumgr *smumgr)
 		return -EINVAL;
 
 	cz_smu = (struct cz_smumgr *)smumgr->backend;
-	if (!cz_smu) {
+	if (cz_smu) {
 		cgs_free_gpu_mem(smumgr->device,
 				cz_smu->toc_buffer.handle);
 		cgs_free_gpu_mem(smumgr->device,