Bluetooth: hci_qca: Deassert RTS while baudrate change command

This patch will help to stop frame reassembly errors while changing
the baudrate. This is because host send a change baudrate request
command to the chip with 115200 bps, Whereas chip will change their
UART clocks to the enable for new baudrate and sends the response
for the change request command with newer baudrate, On host side
we are still operating in 115200 bps which results of reading garbage
data. Here we are pulling RTS line, so that chip we will wait to send data
to host until host change its baudrate.

Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>