iio: cros_ec_sensors: Flush when changing the FIFO timeout

|hwfifo_timeout| is used by the EC firmware only when new samples are
available.
When the timeout changes, espcially when the new timeout is shorter than
the current one, send the samples waiting in the FIFO to the host.
Inline the call to transmit |hwfifo_timeout| value to the firmware.

Now flush when a sensor is suspended (ODR set to 0) as well.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://patch.msgid.link/20250423220506.2061021-1-gwendal@chromium.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>