[POWERPC] powermac: Constify & voidify get_property()

Now that get_property() returns a void *, there's no need to cast its
return value. Also, treat the return value as const, so we can
constify get_property later.

powermac platform & macintosh driver changes.

Built for pmac32_defconfig, g5_defconfig

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/smu.h b/include/asm-powerpc/smu.h
index 51e65fc..e49f644 100644
--- a/include/asm-powerpc/smu.h
+++ b/include/asm-powerpc/smu.h
@@ -517,7 +517,7 @@
  * This returns the pointer to an SMU "sdb" partition data or NULL
  * if not found. The data format is described below
  */
-extern struct smu_sdbp_header *smu_get_sdb_partition(int id,
+extern const struct smu_sdbp_header *smu_get_sdb_partition(int id,
 					unsigned int *size);
 
 /* Get "sdb" partition data from an SMU satellite */