ARM: dts: exynos: add needs-hpd for Odroid-XU3/4

CEC support was added for Exynos5 in 4.13, but for the Odroids we need to set
'needs-hpd' as well since CEC is disabled when there is no HDMI hotplug signal,
just as for the exynos4 Odroid-U3.

This is due to the level-shifter that is disabled when there is no HPD, thus
blocking the CEC signal as well. Same close-but-no-cigar board design as the
Odroid-U3.

Tested with my Odroid XU4.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>