powerpc: Const-qualify Device Node Argument to DCR Resource Extent API

Add const qualifier to device_node argument for
dcr_resource_{start,len} as of_get_property also const-qualifies this
argument.
Signed-off-by: Grant Erickson <gerickson@nuovations.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/include/asm/dcr.h

@@ -68,9 +68,9 @@ typedef dcr_host_mmio_t dcr_host_t;
  * additional helpers to read the DCR * base from the device-tree
  */
 struct device_node;
-extern unsigned int dcr_resource_start(struct device_node *np,
+extern unsigned int dcr_resource_start(const struct device_node *np,
 				       unsigned int index);
-extern unsigned int dcr_resource_len(struct device_node *np,
+extern unsigned int dcr_resource_len(const struct device_node *np,
 				     unsigned int index);
 #endif /* CONFIG_PPC_DCR */
 #endif /* __ASSEMBLY__ */

arch/powerpc/sysdev/dcr.c

@@ -124,7 +124,8 @@ EXPORT_SYMBOL_GPL(dcr_write_generic);
 
 #endif /* defined(CONFIG_PPC_DCR_NATIVE) && defined(CONFIG_PPC_DCR_MMIO) */
 
-unsigned int dcr_resource_start(struct device_node *np, unsigned int index)
+unsigned int dcr_resource_start(const struct device_node *np,
+				unsigned int index)
 {
 	unsigned int ds;
 	const u32 *dr = of_get_property(np, "dcr-reg", &ds);
@@ -136,7 +137,7 @@ unsigned int dcr_resource_start(struct device_node *np, unsigned int index)
 }
 EXPORT_SYMBOL_GPL(dcr_resource_start);
 
-unsigned int dcr_resource_len(struct device_node *np, unsigned int index)
+unsigned int dcr_resource_len(const struct device_node *np, unsigned int index)
 {
 	unsigned int ds;
 	const u32 *dr = of_get_property(np, "dcr-reg", &ds);