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

The Exynos5250 Snow Chromebooks have a Marvell WiFi SDIO chip which
can't neither be removed nor be detected. But the node isn't marked
as non-removable and instead has the broken-cd DT property.

This causes the device to be removed when the system enters into a
suspend state and the following warnings is shown after a resume:

[  181.944636] mmc2: error -2 during resume (card was removed?)

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>