powerpc/powernv: Fix a warning message

Fix a cut'n'paste error in a warning message. This should be
'cpu-idle-state-residency-ns' to match the property searched in the
previous 'of_property_read_u32_array()'

Fixes: 9c7b185a ("powernv/cpuidle: Parse dt idle properties into global structure")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200502115949.139000-1-christophe.jaillet@wanadoo.fr

arch/powerpc/platforms/powernv/idle.c

@@ -1270,7 +1270,7 @@ static int pnv_parse_cpuidle_dt(void)
 	/* Read residencies */
 	if (of_property_read_u32_array(np, "ibm,cpu-idle-state-residency-ns",
 				       temp_u32, nr_idle_states)) {
-		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-latencies-ns in DT\n");
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-residency-ns in DT\n");
 		rc = -EINVAL;
 		goto out;
 	}