env: Rename common functions related to setenv()

We are now using an env_ prefix for environment functions. Rename these
commonly used functions, for consistency. Also add function comments in
common.h.

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/reiser.c

@@ -157,7 +157,7 @@ int do_reiserload (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	load_addr = addr;
 
 	printf ("\n%ld bytes read\n", filelen);
-	setenv_hex("filesize", filelen);
+	env_set_hex("filesize", filelen);
 
 	return filelen;
 }