ui/cocoa: Clean up global variable shadowing

ui/cocoa: Clean up global variable shadowing

Fix:

  ui/cocoa.m:346:20: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
      QemuCocoaView *cocoaView = userInfo;
                     ^
  ui/cocoa.m:342:16: note: previous declaration is here
  QemuCocoaView *cocoaView;
                 ^

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231004120019.93101-11-philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>