[POWERPC] silence a warning

Left over from the constifying of get_property.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
diff --git a/arch/powerpc/platforms/powermac/cpufreq_64.c b/arch/powerpc/platforms/powermac/cpufreq_64.c
index 167cd3c..d30466d 100644
--- a/arch/powerpc/platforms/powermac/cpufreq_64.c
+++ b/arch/powerpc/platforms/powermac/cpufreq_64.c
@@ -89,7 +89,7 @@
 
 #ifdef CONFIG_PMAC_SMU
 
-static u32 *g5_pmode_data;
+static const u32 *g5_pmode_data;
 static int g5_pmode_max;
 
 static struct smu_sdbp_fvt *g5_fvt_table;	/* table of op. points */