ACPICA: Fix compiler warnings for casting issues (only some compilers)

Fixes compiler warnings from GCC 4.2 and perhaps other compilers.
Jung-uk Kim <jkim@FreeBSD.org>

Signed-off-by: Jung-uk Kim <jkim@FreeBSD.org>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/acpi/acpica/exdump.c b/drivers/acpi/acpica/exdump.c
index c740f24..4d046fa 100644
--- a/drivers/acpi/acpica/exdump.c
+++ b/drivers/acpi/acpica/exdump.c
@@ -338,6 +338,7 @@
 {
 	u8 *target;
 	char *name;
+	const char *reference_name;
 	u8 count;
 
 	if (!info) {
@@ -426,10 +427,9 @@
 
 		case ACPI_EXD_REFERENCE:
 
+			reference_name = acpi_ut_get_reference_name(obj_desc);
 			acpi_ex_out_string("Class Name",
-					   ACPI_CAST_PTR(char,
-							 acpi_ut_get_reference_name
-							 (obj_desc)));
+					   ACPI_CAST_PTR(char, reference_name));
 			acpi_ex_dump_reference_obj(obj_desc);
 			break;