platform: goldfish: pipe: Make symbol 'goldfish_pipe_dev' static

Fixes the following sparse warning:

drivers/platform/goldfish/goldfish_pipe.c:214:26: warning:
 symbol 'goldfish_pipe_dev' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/platform/goldfish/goldfish_pipe.c

@@ -210,7 +210,7 @@ struct goldfish_pipe_dev {
 	unsigned char __iomem *base;
 };
 
-struct goldfish_pipe_dev goldfish_pipe_dev;
+static struct goldfish_pipe_dev goldfish_pipe_dev;
 
 static int goldfish_pipe_cmd_locked(struct goldfish_pipe *pipe,
 				    enum PipeCmdCode cmd)