env: Rename some other getenv()-related functions

We are now using an env_ prefix for environment functions. Rename these
other functions as well, for consistency:

   getenv_vlan()
   getenv_bootm_size()
   getenv_bootm_low()
   getenv_bootm_mapsize()
   env_get_default()

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 2210c57..e9dbedf 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -62,8 +62,8 @@
 
 	/* update only when the environment has changed */
 	if (env_changed_id != env_id) {
-		netmask = getenv_ip("netmask");
-		our_ip = getenv_ip("ipaddr");
+		netmask = env_get_ip("netmask");
+		our_ip = env_get_ip("ipaddr");
 
 		env_changed_id = env_id;
 	}
@@ -83,7 +83,7 @@
 	/* update only when the environment has changed */
 	if (env_changed_id != env_id) {
 		if (env_get("ncip")) {
-			nc_ip = getenv_ip("ncip");
+			nc_ip = env_get_ip("ncip");
 			if (!nc_ip.s_addr)
 				return -1;	/* ncip is 0.0.0.0 */
 			p = strchr(env_get("ncip"), ':');