drivers/mmc: Move dereference after NULL test

If the NULL test on mrq is needed, then the derefernce should be after the
NULL test.

A simplified version of the semantic match that detects this problem is as
follows (http://coccinelle.lip6.fr/):

// <smpl>
@match exists@
expression x, E;
identifier fld;
@@

* x->fld
  ... when != \(x = E\|&x\)
* x == NULL
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/s3cmci.c

@@ -820,7 +820,7 @@ static void s3cmci_dma_done_callback(struct s3c2410_dma_chan *dma_ch,
 static void finalize_request(struct s3cmci_host *host)
 {
 	struct mmc_request *mrq = host->mrq;
-	struct mmc_command *cmd = host->cmd_is_stop ? mrq->stop : mrq->cmd;
+	struct mmc_command *cmd;
 	int debug_as_failure = 0;
 
 	if (host->complete_what != COMPLETION_FINALIZE)
@@ -828,6 +828,7 @@ static void finalize_request(struct s3cmci_host *host)
 
 	if (!mrq)
 		return;
+	cmd = host->cmd_is_stop ? mrq->stop : mrq->cmd;
 
 	if (cmd->data && (cmd->error == 0) &&
 	    (cmd->data->error == 0)) {