drm/amd/pm: remove useless if

Clean the following coccicheck warning:

./drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c:7035:2-4: WARNING: possible
condition with no effect (if == else).
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/legacy-dpm/si_dpm.c

@@ -7032,10 +7032,7 @@ static int si_power_control_set_level(struct amdgpu_device *adev)
 	ret = si_resume_smc(adev);
 	if (ret)
 		return ret;
-	ret = si_set_sw_state(adev);
-	if (ret)
-		return ret;
-	return 0;
+	return si_set_sw_state(adev);
 }
 
 static void si_set_vce_clock(struct amdgpu_device *adev,