nand: fix bug with multiple NAND devices if CONFIG_MTD_DEVICE is defined.

The variable i has to be static, otherwise it would be always zero.

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
diff --git a/drivers/mtd/nand/nand.c b/drivers/mtd/nand/nand.c
index c0e068a..d987f4c 100644
--- a/drivers/mtd/nand/nand.c
+++ b/drivers/mtd/nand/nand.c
@@ -43,7 +43,7 @@
 			   ulong base_addr)
 {
 	int maxchips = CONFIG_SYS_NAND_MAX_CHIPS;
-	int __attribute__((unused)) i = 0;
+	static int __attribute__((unused)) i = 0;
 
 	if (maxchips < 1)
 		maxchips = 1;