Since there is no txdone irq in the Rockchip mailbox IP, invoking
mbox_chan_txdone()/mbox_client_txdone() after mbox_send_message()
to tick the TX would be free the active request which have not been
sent out if the controller returned the EBUSY state before. So amend
the txdone method to polling to fix it.
The TX polling interval can specify in DT with
"rockchip,txpoll-period-ms" property, if it is not set, the driver
would hardcode to 5 milliseconds.
Change-Id: Ic26d3245dd8bd90ebad30fce9ece2f4452814f7f
Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
c3ee4f9954