mtd: nand: davinci_nand: correct keystone RBL layout definition

In case when 4K page keystone RBL layout is used the compilation
error is appeared. That's because the #ifdef has to be placed under
struct name. This patch correct it.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>

drivers/mtd/nand/davinci_nand.c

@@ -306,8 +306,8 @@ static struct nand_ecclayout nand_davinci_4bit_layout_oobfirst = {
 };
 
 #if defined CONFIG_KEYSTONE_RBL_NAND
-#if defined(CONFIG_SYS_NAND_PAGE_2K)
 static struct nand_ecclayout nand_keystone_rbl_4bit_layout_oobfirst = {
+#if defined(CONFIG_SYS_NAND_PAGE_2K)
 	.eccbytes = 40,
 	.eccpos = {
 		6, 7, 8, 9, 10, 11, 12, 13, 14, 15,