Mark ui_print with __printflike.

And fix an issue as a result of the change.

Test: mmma -j bootable/recovery
Change-Id: I94e6384a1f39e9c37a8ed029d235142738d6e5d3
(cherry picked from commit 8af89c3a02c1bf358fc3c3b4e0a7cedc8f48631e)

common.h

@@ -40,7 +40,7 @@ extern const char* reason;
 // fopen a file, mounting volumes and making parent dirs as necessary.
 FILE* fopen_path(const std::string& path, const char* mode);
 
-void ui_print(const char* format, ...);
+void ui_print(const char* format, ...) __printflike(1, 2);
 
 bool is_ro_debuggable();