env_mmc: fix cannot save env issue

The env change its implementation after this log, while env mmc
didn't change it immediately, which cause issue. Follow to the
new style to fix it.

commit ea882baf9c17cd142c99e3ff640d3ab01daa5cec
Author: Wolfgang Denk <wd@denx.de>
Date:   Sun Jun 20 23:33:59 2010 +0200

    New implementation for internal handling of environment variables.

Signed-off-by: Lei Wen <leiwen@marvell.com>

common/env_mmc.c

@@ -29,6 +29,7 @@
 #include <linux/stddef.h>
 #include <malloc.h>
 #include <mmc.h>
+#include <errno.h>
 
 /* references to names in env_common.c */
 extern uchar default_environment[];
@@ -96,13 +97,23 @@ inline int write_env(struct mmc *mmc, unsigned long size,
 
 int saveenv(void)
 {
+	env_t	env_new;
+	ssize_t	len;
+	char	*res;
 	struct mmc *mmc = find_mmc_device(CONFIG_SYS_MMC_ENV_DEV);
 
 	if (init_mmc_for_env(mmc))
 		return 1;
 
+	res = (char *)&env_new.data;
+	len = hexport('\0', &res, ENV_SIZE);
+	if (len < 0) {
+		error("Cannot export environment: errno = %d\n", errno);
+		return 1;
+	}
+	env_new.crc   = crc32(0, env_new.data, ENV_SIZE);
 	printf("Writing to MMC(%d)... ", CONFIG_SYS_MMC_ENV_DEV);
-	if (write_env(mmc, CONFIG_ENV_SIZE, CONFIG_ENV_OFFSET, env_ptr)) {
+	if (write_env(mmc, CONFIG_ENV_SIZE, CONFIG_ENV_OFFSET, (u_char *)&env_new)) {
 		puts("failed\n");
 		return 1;
 	}