dt-bindings: mmc: fsl-imx-esdhc: add i.MX8MP compatible string

Add compatible string for imx8mp

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1578893602-14395-2-git-send-email-Anson.Huang@nxp.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>