brcmfmac: finalize transmit upon any rollback failure

All rollback failures should result in freeing of the sk_buff
by calling brcmf_txfinalize().

Reviewed-by: Hante Meuleman <meuleman@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>