ahci: ahci_p5wdh_workaround - constify DMI table

The DMI table does not need to be written to, make it r/o.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index a29f801..c880699 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -780,7 +780,7 @@
  */
 static void ahci_p5wdh_workaround(struct ata_host *host)
 {
-	static struct dmi_system_id sysids[] = {
+	static const struct dmi_system_id sysids[] = {
 		{
 			.ident = "P5W DH Deluxe",
 			.matches = {