ARM: dts: Mark eMMC as non-removable in exynos5250-snow-common

The eMMC is non-removable so mark it using the non-removable DT
property to avoid having to redetect it after a suspend/resume.

Also remove the card-detect-delay property that is not needed with
non-removable.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Tested-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>