edje_recc: don't use negative exit code in a /bin/sh script

Apparently this isn't well supported by dash, which will print an
error and return a 2, where zsh and bash will return 255.

Explicitly returning 255 seems least surprising.

see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=772322

 #IHaveNoIdeaWhatThisScriptDoes

src/bin/edje/edje_recc

@@ -14,7 +14,7 @@ usage () {
   echo "-no-raw                  Do NOT allow images to be zero compression"
   echo "-min-quality VAL         Do NOT allow lossy images with quality < VAL (0-100)"
   echo "-max-quality VAL         Do NOT allow lossy images with quality > VAL (0-100)"
-  exit -1
+  exit 255
 }
 
 if [ $# -lt 1 ]; then