ARM: dts: Make DP a consumer of DISP1 power domain on Exynos5420

Commit ea08de16 ("ARM: dts: Add DISP1 power domain for exynos5420")
added a device node for the Exynos5420 DISP1 power domain but dit not
make the DP controller a consumer of that power domain.

This causes an "Unhandled fault: imprecise external abort" error if the
exynos-dp driver tries to access the DP controller registers and the PD
was turned off. This lead to a kernel panic and a complete system hang.

Make the DP controller device node a consumer of the DISP1 power domain
to ensure that the PD is turned on when the exynos-dp driver is probed.

Fixes: ea08de16 ("ARM: dts: Add DISP1 power domain for exynos5420")
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Kukjin Kim <kgene@kernel.org>