ARM: EXYNOS: Fix compilation warning

of_get_flat_dt_prop return type is now const.
Fixes the following compilation warning introduced by commit 9d0c4dfedd96
("of/fdt: update of_get_flat_dt_prop in prep for libfdt")

arch/arm/mach-exynos/exynos.c:259:6: warning:
assignment discards ‘const’ qualifier from pointer target type [enabled by default]

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Reviewed-by: Tushar Behera <tushar.behera@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-exynos/exynos.c

@@ -220,7 +220,7 @@ static int __init exynos_fdt_map_chipid(unsigned long node, const char *uname,
 					int depth, void *data)
 {
 	struct map_desc iodesc;
-	__be32 *reg;
+	const __be32 *reg;
 	int len;
 
 	if (!of_flat_dt_is_compatible(node, "samsung,exynos4210-chipid") &&