Split increments to silence a compiler warning.

Upstream clang complains that this line may be a possible misuse of the
comma operator, since the result from "p++" is being discarded. Rather
than overcomplicate things with a static_cast<void>(), it is easiest to
just move this to a separate statement.

Change-Id: I5d005eb82a02430f691f99a2f1e8b7237320f84a
diff --git a/libs/ui/Region.cpp b/libs/ui/Region.cpp
index a3558bd..f7087a9 100644
--- a/libs/ui/Region.cpp
+++ b/libs/ui/Region.cpp
@@ -489,7 +489,8 @@
                     merge = false;
                     break;
                 }
-                p++, q++;
+                p++;
+                q++;
             }
         }
     }