brcmfmac: fix memory leakage in msgbuf

The kbuild robot came up with the following warning:

tree:   .../kernel/git/linville/wireless-next.git master
head:   dc6be9f
commit: 9a1bb60
	 [5/13] brcmfmac: Adding msgbuf protocol.

coccinelle warnings:
 drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c:1309:1-28:
   alloc with no test, possible model on line 1318

Looking into the issue, it turned out that the referred allocation
buffer was not being released in failure path nor upon module
unload.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/msgbuf.c

@@ -1318,6 +1318,8 @@ int brcmf_proto_msgbuf_attach(struct brcmf_pub *drvr)
 	msgbuf->nrof_flowrings = if_msgbuf->nrof_flowrings;
 	msgbuf->flowring_dma_handle = kzalloc(msgbuf->nrof_flowrings *
 		sizeof(*msgbuf->flowring_dma_handle), GFP_ATOMIC);
+	if (!msgbuf->flowring_dma_handle)
+		goto fail;
 
 	msgbuf->rx_dataoffset = if_msgbuf->rx_dataoffset;
 	msgbuf->max_rxbufpost = if_msgbuf->max_rxbufpost;
@@ -1362,6 +1364,7 @@ int brcmf_proto_msgbuf_attach(struct brcmf_pub *drvr)
 		kfree(msgbuf->flow_map);
 		kfree(msgbuf->txstatus_done_map);
 		brcmf_msgbuf_release_pktids(msgbuf);
+		kfree(msgbuf->flowring_dma_handle);
 		if (msgbuf->ioctbuf)
 			dma_free_coherent(drvr->bus_if->dev,
 					  BRCMF_TX_IOCTL_MAX_MSG_SIZE,
@@ -1391,6 +1394,7 @@ void brcmf_proto_msgbuf_detach(struct brcmf_pub *drvr)
 				  BRCMF_TX_IOCTL_MAX_MSG_SIZE,
 				  msgbuf->ioctbuf, msgbuf->ioctbuf_handle);
 		brcmf_msgbuf_release_pktids(msgbuf);
+		kfree(msgbuf->flowring_dma_handle);
 		kfree(msgbuf);
 		drvr->proto->pd = NULL;
 	}