ASoC: esai: use the precise definition of 'ret'.

Use the precise definition of 'ret', which will be used for
the error check.

Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
Acked-by: Nicolin Chen <Guangyu.Chen@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>