board: constify struct node_info array

Add 'const' (also 'static' in some places) to struct node_info
arrays to save memory footprint.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/board/gateworks/gw_ventana/gw_ventana.c b/board/gateworks/gw_ventana/gw_ventana.c
index b86924e..c4ec974 100644
--- a/board/gateworks/gw_ventana/gw_ventana.c
+++ b/board/gateworks/gw_ventana/gw_ventana.c
@@ -1114,7 +1114,7 @@
 {
 	struct ventana_board_info *info = &ventana_info;
 	struct ventana_eeprom_config *cfg;
-	struct node_info nodes[] = {
+	static const struct node_info nodes[] = {
 		{ "sst,w25q256",          MTD_DEV_TYPE_NOR, },  /* SPI flash */
 		{ "fsl,imx6q-gpmi-nand",  MTD_DEV_TYPE_NAND, }, /* NAND flash */
 	};