brcmfmac: Correct creditmap when credit borrowing is active.

When credit borrowing is active the BE credits have been depleted,
however the worker should still be scheduled. In case of credit
borrowing correct credit map to make sure worker remains active.

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