Improves travis buildroot regexp

buildroot/bin/opt_set_adv

@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 
-eval "sed -i 's/\(#define +$1 +\)[^ ]*$/\1 $2/g' Marlin/Configuration_adv.h"
+eval "sed -i 's/\(#define \b${1}\b\).*$/\1 ${2}/g' Marlin/Configuration_adv.h"