env_nand: Updated erase size to partition size

erase complete partiton size, board_env_size.

Change-Id: Ib0f7e65f49fbd29cd265f5ff12cd03424db61227
Signed-off-by: Gokul Sriram Palanisamy <gokulsri@codeaurora.org>
diff --git a/common/env_nand.c b/common/env_nand.c
index 61096b8..d1f617a 100644
--- a/common/env_nand.c
+++ b/common/env_nand.c
@@ -189,7 +189,7 @@
 		{
 			.name = "NAND",
 			.erase_opts = {
-				.length = CONFIG_ENV_RANGE,
+				.length = board_env_size,
 				.offset = CONFIG_ENV_OFFSET,
 			},
 		},