Make setenv() return status

Currently, the setenv function does not return an error code.
This patch allows to test for errors.

Signed-off-by: Steve Falco <sfalco@harris.com>
diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index 49f134a..b102ae3 100644
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -380,13 +380,13 @@
 	return 0;
 }
 
-void setenv (char *varname, char *varvalue)
+int setenv (char *varname, char *varvalue)
 {
 	char *argv[4] = { "setenv", varname, varvalue, NULL };
 	if (varvalue == NULL)
-		_do_setenv (0, 2, argv);
+		return _do_setenv (0, 2, argv);
 	else
-		_do_setenv (0, 3, argv);
+		return _do_setenv (0, 3, argv);
 }
 
 #ifdef CONFIG_HAS_UID