When changing the audio hw params, reset the audio fifo to make sure
any old remaining data is flushed.

The databook mentions that such reset should be followed by a reset of
the i2s block to make sure the samples stay aligned
Reviewed-by: NJonas Karlman <jonas@kwiboo.se>
Signed-off-by: NJerome Brunet <jbrunet@baylibre.com>
Reviewed-by: NNeil Armstrong <narmstrong@baylibre.com>
Signed-off-by: NNeil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190812120726.1528-7-jbrunet@baylibre.com