env: Add env_export() wrapper

Implement env_export() wrapper, so that all implementers of saveenv() don't
have to call hexport_r(), crc32() etc. sequence . This trims down a bit of
code duplication.

Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/common/env_eeprom.c b/common/env_eeprom.c
index 0db2bb6..490ac73 100644
--- a/common/env_eeprom.c
+++ b/common/env_eeprom.c
@@ -98,8 +98,6 @@
 int saveenv(void)
 {
 	env_t	env_new;
-	ssize_t	len;
-	char	*res;
 	int	rc;
 	unsigned int off	= CONFIG_ENV_OFFSET;
 #ifdef CONFIG_ENV_OFFSET_REDUND
@@ -109,13 +107,9 @@
 
 	BUG_ON(env_ptr != NULL);
 
-	res = (char *)&env_new.data;
-	len = hexport_r(&env_htab, '\0', 0, &res, ENV_SIZE, 0, NULL);
-	if (len < 0) {
-		error("Cannot export environment: errno = %d\n", errno);
-		return 1;
-	}
-	env_new.crc = crc32(0, env_new.data, ENV_SIZE);
+	rc = env_export(&env_new);
+	if (rc)
+		return rc;
 
 #ifdef CONFIG_ENV_OFFSET_REDUND
 	if (gd->env_valid == 1) {