brcm80211: smac: eliminate a null pointer dereference in dma.c

Though it's unlikely, di may be null, so we can't dereference
di->dma.dmactrlflags until we've checked it.

Move this de-reference after the check, and adjust the error
message to not require de-referencing di.

This is based upon Julia's original patch:
<1319846297-2985-2-git-send-email-julia@diku.dk>
Reported-by: NJulia Lawall <julia@diku.dk>
Acked-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NJulian Calaby <julian.calaby@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmsmac/dma.c

@@ -358,13 +358,14 @@ static uint nrxdactive(struct dma_info *di, uint h, uint t)
 
 static uint _dma_ctrlflags(struct dma_info *di, uint mask, uint flags)
 {
-	uint dmactrlflags = di->dma.dmactrlflags;
+	uint dmactrlflags;
 
 	if (di == NULL) {
-		DMA_ERROR(("%s: _dma_ctrlflags: NULL dma handle\n", di->name));
+		DMA_ERROR(("_dma_ctrlflags: NULL dma handle\n"));
 		return 0;
 	}
 
+	dmactrlflags = di->dma.dmactrlflags;
 	dmactrlflags &= ~mask;
 	dmactrlflags |= flags;