reset: uniphier: add video input subsystem reset control

Add a reset line for video input subsystem (EXIV) on
UniPhier LD11/LD20 SoCs.

Signed-off-by: Katsuhiro Suzuki <suzuki.katsuhiro@socionext.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>