brcmfmac: check brcmf_bus_get_memdump result for error

This method may be unsupported (see: USB bus) or may just fail (see:
SDIO bus).
While at it rework logic in brcmf_sdio_bus_get_memdump function to avoid
too many conditional code nesting levels.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/broadcom/brcm80211/brcmfmac/debug.c

@@ -32,16 +32,25 @@ static int brcmf_debug_create_memdump(struct brcmf_bus *bus, const void *data,
 {
 	void *dump;
 	size_t ramsize;
+	int err;
 
 	ramsize = brcmf_bus_get_ramsize(bus);
-	if (ramsize) {
-		dump = vzalloc(len + ramsize);
-		if (!dump)
-			return -ENOMEM;
-		memcpy(dump, data, len);
-		brcmf_bus_get_memdump(bus, dump + len, ramsize);
-		dev_coredumpv(bus->dev, dump, len + ramsize, GFP_KERNEL);
+	if (!ramsize)
+		return -ENOTSUPP;
+
+	dump = vzalloc(len + ramsize);
+	if (!dump)
+		return -ENOMEM;
+
+	memcpy(dump, data, len);
+	err = brcmf_bus_get_memdump(bus, dump + len, ramsize);
+	if (err) {
+		vfree(dump);
+		return err;
 	}
+
+	dev_coredumpv(bus->dev, dump, len + ramsize, GFP_KERNEL);
+
 	return 0;
 }