brcmfmac: stop dequeue upon sk_buff commit failure

In the dequeue worker the function brcmf_commit_skb() is called.
However, instead of increment the credit count upon success it
should break the for loop upon failure. Otherwise, it will result
in an endless loop.

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>