msm: kgsl: Power scale policy needs at least three power levels.

Since 7x25A supports two power levels, do not allow it to register
with the power scale policy.

Change-Id: I1a77f0aa8e7affa126d7c18cb2d73e8617602dcf
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>
diff --git a/drivers/gpu/msm/kgsl_pwrscale.c b/drivers/gpu/msm/kgsl_pwrscale.c
index 928ea65..55e5383 100644
--- a/drivers/gpu/msm/kgsl_pwrscale.c
+++ b/drivers/gpu/msm/kgsl_pwrscale.c
@@ -297,6 +297,11 @@
 	if (device->pwrscale.policy == policy)
 		goto done;
 
+	if (device->pwrctrl.num_pwrlevels < 3) {
+		ret = -EINVAL;
+		goto done;
+	}
+
 	if (device->pwrscale.policy != NULL)
 		_kgsl_pwrscale_detach_policy(device);