mailbox: arm_mhuv2: Constify amba_id table

'struct amba_id' table is not modified so can be changed to const for
more safety.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>

drivers/mailbox/arm_mhuv2.c

···
 		writel_relaxed(0x0, &mhu->send->access_request);
 }
 
-static struct amba_id mhuv2_ids[] = {
+static const struct amba_id mhuv2_ids[] = {
 	{
 		/* 2.0 */
 		.id = 0xbb0d1,