ARM: dts: use 'status' property for PCIe nodes

Set the default status for PCIe to disabled in the exynos5440.dtsi
file and let the board dts files such as exynos5440-ssdk5440.dts
enable the PCIe. However, keep the PCIe for SD5v1 board disabled,
because there is no PCIe slot on SD5v1 board.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>