dt-bindings: mmc: sdhci-of-arasan: Add new compatible for Intel LGM eMMC

Add a new compatible to use the sdhc-arasan host controller driver
with the eMMC PHY on Intel's Lightning Mountain SoC.

Signed-off-by: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@linux.intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>