brcmsmac: Fix possible NULL pointer dereference in _dma_ctrlflags()

There's a debug message to warn if this function is passed a NULL
pointer, but in order to print the message we have to dereference the
pointer. Obviously this isn't a good idea, so remove the message.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -349,10 +349,8 @@ static uint _dma_ctrlflags(struct dma_info *di, uint mask, uint flags)
 {
 	uint dmactrlflags;
 
-	if (di == NULL) {
-		brcms_dbg_dma(di->core, "NULL dma handle\n");
+	if (di == NULL)
 		return 0;
-	}
 
 	dmactrlflags = di->dma.dmactrlflags;
 	dmactrlflags &= ~mask;