of/fdt: fix sparse warning

this patch fixes following sparse warning:

fdt.c:765:12: warning: symbol 'early_init_dt_scan_chosen_serial' was not declared. Should it be static?

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 5100742..3a896c9 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -762,7 +762,7 @@
 #ifdef CONFIG_SERIAL_EARLYCON
 extern struct of_device_id __earlycon_of_table[];
 
-int __init early_init_dt_scan_chosen_serial(void)
+static int __init early_init_dt_scan_chosen_serial(void)
 {
 	int offset;
 	const char *p;