phb4: Fix GEN3 for DD2.00

In this fix:
  62ac763 phb4: Fix PCIe GEN4 on DD2.1 and above
We fixed DD2.1 GEN4 but broke DD2.00 as GEN3.

This fixes DD2.00 back to GEN3. This time for sure!

Signed-off-by: Michael Neuling <mikey@neuling.org>
Tested-by: Pridhiviraj Paidipeddi <ppaidipe@linux.vnet.ibm.com>

hw/phb4.c

@@ -4900,7 +4900,7 @@ static void phb4_create(struct dt_node *np)
 	if (p->rev == PHB4_REV_NIMBUS_DD10)
 		p->max_link_speed = 2;
 	if (p->rev == PHB4_REV_NIMBUS_DD20 &&
-	    chip->ec_level == 0 && chip->ec_rev == 0)
+	    ((0xf & chip->ec_level) == 0) && chip->ec_rev == 0)
 		p->max_link_speed = 3;
 	if (dt_has_node_property(np, "ibm,max-link-speed", NULL))
 		p->max_link_speed = dt_prop_get_u32(np, "ibm,max-link-speed");