ASoC: SOF: imx8: Make some functions static

ASoC: SOF: imx8: Make some functions static

Fix sparse warnings:

sound/soc/sof/imx/imx8.c:104:6: warning: symbol 'imx8_dsp_handle_reply' was not declared. Should it be static?
sound/soc/sof/imx/imx8.c:115:6: warning: symbol 'imx8_dsp_handle_request' was not declared. Should it be static?
sound/soc/sof/imx/imx8.c:336:5: warning: symbol 'imx8_get_bar_index' was not declared. Should it be static?
sound/soc/sof/imx/imx8.c:341:6: warning: symbol 'imx8_ipc_msg_data' was not declared. Should it be static?
sound/soc/sof/imx/imx8.c:348:5: warning: symbol 'imx8_ipc_pcm_params' was not declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
Link: https://lore.kernel.org/r/20190823125939.30012-1-yuehaibing@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>