brcmfmac: assure brcmf_txcomplete() is called in failure paths

For transmit packets the function brcmf_txcomplete() must be
called. This should be done as well when for some reason the
transmit fails to assure proper tx post processing. This patch
fixes the code paths in brcmf_usb_tx() that forgot to do so.

Reviewed-by: Piotr Haber <phaber@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>