Fix incorrect use of getenv() before relocation

A large number of boards incorrectly used getenv() in their board init
code running before relocation.  In some cases this caused U-Boot to
hang when certain environment variables grew too long.
Fix the code to use getenv_r().

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: The LEOX team <team@leox.org>
Cc: Michael Schwingen <michael@schwingen.org>
Cc: Georg Schardt <schardt@team-ctech.de>
Cc: Werner Pfister <Pfister_Werner@intercontrol.de>
Cc: Dirk Eibach <eibach@gdsys.de>
Cc: Peter De Schrijver <p2@mind.be>
Cc: John Zhan <zhanz@sinovee.com>
Cc: Rishi Bhattacharya <rishi@ti.com>
Cc: Peter Tyser <ptyser@xes-inc.com>
diff --git a/board/digsy_mtc/digsy_mtc.c b/board/digsy_mtc/digsy_mtc.c
index 9f13a3d..588face 100644
--- a/board/digsy_mtc/digsy_mtc.c
+++ b/board/digsy_mtc/digsy_mtc.c
@@ -191,15 +191,16 @@
 
 int checkboard(void)
 {
-	char *s = getenv("serial#");
+	char buf[64];
+	int i = getenv_f("serial#", buf, sizeof(buf));
 
 	puts ("Board: InterControl digsyMTC");
 #if defined(CONFIG_DIGSY_REV5)
 	puts (" rev5");
 #endif
-	if (s != NULL) {
+	if (i > 0) {
 		puts(", ");
-		puts(s);
+		puts(buf);
 	}
 	putc('\n');