brcmfmac: correct specified length from FIFOCREDITBACK signal

The length is not according specification so better fix it.
Reviewed-by: NPieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: NPiotr Haber <phaber@broadcom.com>
Reviewed-by: NHante Meuleman <meuleman@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

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

@@ -59,7 +59,7 @@
 	BRCMF_FWS_TLV_DEF(RSSI, 8, 1) \
 	BRCMF_FWS_TLV_DEF(INTERFACE_OPEN, 9, 1) \
 	BRCMF_FWS_TLV_DEF(INTERFACE_CLOSE, 10, 1) \
-	BRCMF_FWS_TLV_DEF(FIFO_CREDITBACK, 11, 8) \
+	BRCMF_FWS_TLV_DEF(FIFO_CREDITBACK, 11, 6) \
 	BRCMF_FWS_TLV_DEF(PENDING_TRAFFIC_BMP, 12, 2) \
 	BRCMF_FWS_TLV_DEF(MAC_REQUEST_PACKET, 13, 3) \
 	BRCMF_FWS_TLV_DEF(HOST_REORDER_RXPKTS, 14, 10) \