ASoC: fsl_esai doc: Add "fsl,vf610-esai" as compatible string

Since commit b21cc2f5 ("ASoC: esai: Add VF610+ compatibles support.")
the fsl_esai driver also accepts  the "fsl,vf610-esai" compatible string.

Update the documentation accordingly.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>