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/board/freescale/p2041rdb/p2041rdb.c b/board/freescale/p2041rdb/p2041rdb.c
index 21fb66f..78ee747 100644
--- a/board/freescale/p2041rdb/p2041rdb.c
+++ b/board/freescale/p2041rdb/p2041rdb.c
@@ -219,8 +219,8 @@
 
 	ft_cpu_setup(blob, bd);
 
-	base = getenv_bootm_low();
-	size = getenv_bootm_size();
+	base = env_get_bootm_low();
+	size = env_get_bootm_size();
 
 	fdt_fixup_memory(blob, (u64)base, (u64)size);