brcm80211: Add support for brcm4371

This is a new Broadcom chip and we should be able to recognize it.

Signed-off-by: Eric Caruso <ejcaruso@google.com>
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>