While we now support the internal display pipeline found on sun6i, it
is possible that we are unable to enable the display for some boards,
due to a lack of drivers for the panels or bridges found on them. If
the display pipeline is enabled, the driver will try to enable, and
possibly screw up the simple framebuffer U-boot had configured.

Disable the display pipeline by default.

Fixes: 6d0e5b70 ("ARM: dts: sun6i: Add device nodes for first
		      display pipeline")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>