brcmsmac: Free packet if dma_mapping_error() fails in dma_rxfill

In case dma_mapping_error() returns an error in dma_rxfill, we would be
leaking a packet that we allocated with brcmu_pkt_buf_get_skb().

Reported-by: coverity (CID 1081819)
Fixes: 67d0cf50bd32 ("brcmsmac: Fix WARNING caused by lack of calls to dma_mapping_error()")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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

@@ -1079,8 +1079,10 @@ bool dma_rxfill(struct dma_pub *pub)
 
 		pa = dma_map_single(di->dmadev, p->data, di->rxbufsize,
 				    DMA_FROM_DEVICE);
-		if (dma_mapping_error(di->dmadev, pa))
+		if (dma_mapping_error(di->dmadev, pa)) {
+			brcmu_pkt_buf_free_skb(p);
 			return false;
+		}
 
 		/* save the free packet pointer */
 		di->rxp[rxout] = p;