PixelFormat.UNKNOWN should return an error when queried

Bug: 6294260
Change-Id: Iad6f7bcbdda0a684abca6d9584da611a8b28f7ab
diff --git a/libs/ui/PixelFormat.cpp b/libs/ui/PixelFormat.cpp
index fc1d3c2..3ced41d 100644
--- a/libs/ui/PixelFormat.cpp
+++ b/libs/ui/PixelFormat.cpp
@@ -91,7 +91,7 @@
 
 status_t getPixelFormatInfo(PixelFormat format, PixelFormatInfo* info)
 {
-    if (format < 0)
+    if (format <= 0)
         return BAD_VALUE;
 
     if (info->version != sizeof(PixelFormatInfo))