We don't stop transmissions in progress at shutdown. This is fine with
FIFO SE mode but with DMA (support for which we'll introduce later) it
causes trouble so fix it now.

Fixes: e8376633 ("tty: serial: qcom_geni_serial: No need to stop tx/rx on UART shutdown")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20221229155030.418800-2-brgl@bgdev.plSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>