powerpc/5200: fix oops during going to standby

When going to standby mode mpc code maps the whole soc5200 node
to access warious MBAR registers. However as of_iomap uses 'reg'
property of device node, only small part of MBAR is getting mapped.
Thus pm code gets oops when trying to access high parts of MBAR.
As a way to overcome this, make mpc52xx_pm_prepare() explicitly
map whole MBAR (0xc0000).

Signed-off-by: Dmitry Eremin-Solenikov <[e-mail]>
Signed-off-by: Grant Likely <[e-mail]>

arch/powerpc/platforms/52xx/mpc52xx_pm.c

···
 		{ .type = "builtin", .compatible = "mpc5200", }, /* efika */
 		{}
 	};
+	struct resource res;
 
 	/* map the whole register space */
 	np = of_find_matching_node(NULL, immr_ids);
-	mbar = of_iomap(np, 0);
+
+	if (of_address_to_resource(np, 0, &res)) {
+		pr_err("mpc52xx_pm_prepare(): could not get IMMR address\n");
+		of_node_put(np);
+		return -ENOSYS;
+	}
+
+	mbar = ioremap(res.start, 0xc000); /* we should map whole region including SRAM */
+
 	of_node_put(np);
 	if (!mbar) {
 		pr_err("mpc52xx_pm_prepare(): could not map registers\n");