ARM: dts: Move fifo-depth property from exynos5250 board dts

As fifo-depth property in dw_mmc device tree node is SOC
specific, move this property to exynos5250 SOC specific
file.

Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
[kgene.kim@samsung.com: squashed fifo-depth patch for cros5250-common]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>