mmc: queue: declare mmc_alloc_sg as static

Fix the sparse warning "drivers/mmc/card/queue.c:111:20: warning:
symbol 'mmc_alloc_sg' was not declared. Should it be static?"

Signed-off-by: Venkatraman S <svenkatr@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/card/queue.c

@@ -108,7 +108,7 @@ static void mmc_request(struct request_queue *q)
 		wake_up_process(mq->thread);
 }
 
-struct scatterlist *mmc_alloc_sg(int sg_len, int *err)
+static struct scatterlist *mmc_alloc_sg(int sg_len, int *err)
 {
 	struct scatterlist *sg;