Bluetooth: Check the tx_window size on setsockopt

We have to check if the proposed tx_window value is not greater that
maximum value supported.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>